The day we meet, the sky is black and the rain comes fast and heavy. Rose McGowan had walked into the hotel bar looking slight, but as she sits in an armchair, her back to the window, streaks of lightning flash outside behind her head and she looks, instead, like some sort of avenging angel. “I wanted to show people around the world that you can strike at the head of power and not just bite at the ankles,” she says. “Because they can shake you off when you bite at the ankles.”

When allegations of sexual assault started to surface about the film producer Harvey Weinstein late last year – he has denied all allegations of nonconsensual sex – McGowan added her voice, early and loudly. The former actor had collaborated with Jodi Kantor and Megan Twohey, the New York Times journalists who broke the story in October, passing on information about the $100,000 settlement he paid her in 1997 after an alleged assault. When Weinstein turned himself in last week, McGowan tweeted: “We got you, Harvey Weinstein, we got you.” This week, a grand jury indicted Weinstein on rape and criminal sex act charges, which he denies.

“I cried the other night, finally,” she says. “I was asked a lot when he was arrested: ‘How does it feel?’ And I hadn’t really had time to process how it felt. I went to Central Park – it was around midnight – and I just cried. I cried for the girl I was, I cried for her. But today I smile for me.”

The aftermath of the story breaking has been “extreme” says McGowan, although she says she had been living through a strange and nightmarish time long before the articles came out. She alleges that, when he heard about her tell-all memoir, Brave, Weinstein hired investigators, including former agents from the Mossad, to follow her and infiltrate her circle. It sounds like an outlandish claim, but a New Yorker story corroborates it. (A Weinstein spokesman told the magazine: “It is a fiction to suggest that any individuals were targeted or suppressed at any time.”)

Weinstein with McGowan in 2007. Photograph: Jeff Vespa/WireImage

McGowan says her arrest in January last year for possession of cocaine – it was found in a wallet she had lost on a plane – is part of the attempt to silence her. A court hearing is scheduled in just over a week. How is she coping? “It’s such a nightmare. And it feels like they’re doing the work of a rapist. It’s truly insane.” Is she prepared for the fact she may go to prison? “No. I refuse. And if they do [imprison her], it’s because they’re trying to silence a woman.” Is she prepared for the fact that Weinstein may not go to prison? She says she thinks the opposite – she thinks about him going to jail.

For McGowan, Weinstein’s fall has been a long time coming. In 2016, she alleged on Twitter that a “studio head” had raped her and she had been working on her memoir – in which she would write about the 1997 assault – for more than three years. The book was finished, and she was proofreading it and sorting out a few legal issues, when the New York Times and New Yorker stories about Weinstein dropped. Would she have published her book without them? “I didn’t want to,” she says. “I would have published it, but my goal was also to bring down a power structure.” She smiles. Without the press reports and other women – including Gwyneth Paltrow, Asia Argento, Mira Sorvino and Salma Hayek – coming forward, “I think it would have largely fallen on deaf ears”.

Society was ready to hear it, she says. “I think [the sexual misconduct allegations against Donald] Trump helped a lot, making it very black-and-white for people. We’ve been saying it for a long time, just like African Americans have been saying they get shot by the police. It was always just a pat on the head: ‘It’s just people complaining.’ No, women are telling the truth.”

One night, four years ago, McGowan was at home during a power cut. She lay in the dark, with time to think and no distractions, and decided she hated acting. “Not the act of acting; I just hated every part of the system I was in,” she says. “It was like an alarm bell going off in my head: ‘Wake up: this life is not right for you.’ And it was like a thunderbolt.” McGowan started behaving with all the freedom of someone who felt they had nothing to lose. In 2015, she tweeted a casting note that came with a script for an Adam Sandler film that asked actresses to show cleavage: “push-up bras encouraged”. She describes it as “the opening salvo”. Her agent fired her.

Then she started giving interviews, talking about the sexism and sexual abuse in the industry. She shaved off her long, dark hair which, she says, had been part of what Hollywood expected of her. “I went up against them. It was just not done, it’s supposed to be sacrosanct,” she says, laughing. She says that someone recently asked if she was persona non grata in Hollywood. “Well, they’re personae non gratae with me. Don’t I get a say?”

She has not behaved the way Hollywood expected her to, but she has also had a tricky relationship with the #MeToo movement. It probably has much to do with how unconventional she is, as well as a sense that she just does not seem to care what people think about her, but there have been eccentric appearances on TV talkshows and a public row with a transgender person at one of her book signings. When attenders at the Golden Globes wore black in solidarity, McGowan responded on Twitter, saying that “not one of those fancy people wearing black to honor our rapes would have lifted a finger” had she and others not spoken up. She has attacked prominent individuals involved in the movement, such as Alyssa Milano, and been accused of self-promotion and glorification. How does she cope with that accusation? “That’s only stupid … people saying that. So I don’t have to cope with them at all. Why would I want this publicity? It’s asinine. If you follow me out on the street, people don’t say that.”

Rose McGowan (centre) with Julie Benz and Judy Greer in Jawbreaker (1999). Photograph: Sportsphoto Ltd/Allstar

Hers is an extraordinary life. Her father, whom she believes had bipolar disorder, came from a chaotic family and, while using heroin in California, joined the religious cult Children of God and came off drugs. Her mother had run away at 15 and met McGowan’s father at 18. By 19, writes McGowan, “she was pregnant and in a cult”.

McGowan was born in Tuscany, into the Italian branch of Children of God. As a child, she was beaten by one of its members because she refused to say she had “let God into [her] heart”. Her younger sister would urge her to lie to spare the punishment, but McGowan stood fast. She was, she writes, a “born dissenter”, furious that nobody would listen to her because she was a child and, in particular, a girl. She claims she witnessed children being sexually abused and women being treated appallingly. When her father left the cult, bringing McGowan back to the US, she was bounced between him and other relatives, eventually being reunited with her mother, who had stayed in Italy but finally also escaped.

The next few years were horrific (my word; she describes it as “tough”), disrupted by the violent and abusive men her mother took up with, an enforced spell in rehab (caused, she says, by her stepfather finding out she had taken a single acid tab) and a period being a homeless runaway. Eventually, she found herself back with her mentally ill father, who wouldn’t give her cutlery or a proper bed because he said she wasn’t worth it. She would fantasise about murdering him, she writes in her book.

It was when he told her she had to pay several hundred dollars a month in rent that she answered an advert asking for movie extras. At 15, she appeared in a film Class of 1999; one of the men involved in the film called her up to his hotel room and allegedly sexually assaulted her. And so began McGowan’s experience of Hollywood. She soon realised, she says, “that town is really built on sickness. Very early on I looked at the power structure, the figureheads, the silence, the closed ranks. Nobody tells. It operates like a cult.” As a woman, she says she felt belittled and objectified, treated as inferior to her male colleagues: “I always knew that I was No 2 on the call sheet instead of No 1, even though I was the lead. Or nobody would listen to anything I would say, even if it could save a lot of money or time on set. I had a line on the inside of my mouth that I would chew, just bite down. Just suck it up, push the rage down.”

It was 1997, during the Sundance film festival, when Weinstein summoned McGowan to his hotel suite. She had starred in the Miramax film Going All the Way and was shooting another, Phantoms. Her manager said she should go and meet him. Thinking the meeting was finished, McGowan writes, she walked down the hallway with Weinstein. Then, she alleges, he pushed her into a small, dark Jacuzzi room, took off her clothes and sexually assaulted her. She says she faked an orgasm to get him to stop.

The complicity and cover-up followed. McGowan says her manager at the time, Jill Messick, told her it “would help her career in the long run”. Weinstein, trying to defend himself, released an email from Messick in January this year in which she said her memory of what happened in 1997 was that it had been consensual, if something McGowan later regretted. Messick had become publicly embroiled in the story and, in February, she killed herself. A statement from her family partly blamed Weinstein and McGowan, claiming that Messick, who had mental health problems, had been devastated by “one person’s attempt to gain more attention for her personal cause, along with Harvey’s desperate attempt to vindicate himself”. McGowan responded with an Instagram post wishing Messick’s family “solace”, adding: “The bad man did this to us both.”

After the alleged assault, McGowan says she approached a lawyer who told her she would never win a court case against him because “you are an actress. You’ve done a sex scene.” Instead, she was given $100,000 by Weinstein – she says the money felt dirty and she gave most of it away.

The result of her efforts, she claims, is that Weinstein blacklisted her and derailed her career. Did she know at the time? “Yes. I thought the people participating in it were disgusting and weak because they knew the truth, but they did it anyway. To me, they’re blacker than he is in a lot of ways. I had an agent who said [a Hollywood executive] had said: ‘Over my dead body will Rose McGowan ever be hired.’”

It was only a couple of nights in my darkest times when I wished I had shut up

She carried on working, though. I wonder why. It would have been appalling to have been hounded out of a job she loved, but, as she notes, she didn’t love it. She says she was famous by then, appearing in the TV series Charmed, and wouldn’t have been able to get another job outside the entertainment industry. I’m not sure this follows. More compelling is the reason she gives in her book: that she was terrified of being homeless again. “Safety isn’t a feeling I have known,” she says, talking about her childhood. “Not unless it’s self-provided.” What kept her going? She smiles. “I always knew I was right and I have always been one for justice.”

She says, with some understatement, that living with the aftermath of the assault and its effect on her career was “hard. I think I splintered off for a long time. You compartmentalise and your sense of self is locked very far away. But it was only a couple of nights in my darkest times when I wished I had shut up back then, usually around the Oscars.” She gives a wry smile. “Because [my career] would have gone in a very different direction had I not [made it] very clear that I don’t like this, I don’t want this.” Could she have imagined staying quiet? “I can’t imagine who that person would be because it would be so not me.”

For five years she appeared in the TV series, Charmed. She didn’t particularly enjoy it, she says, but she says it was a “strategic” move. “It was big all over the world. I joined in the fourth season and it was already a hit. When and if I managed to break this news, it would be newsworthy all over the world because I’d kept my celebrity level just enough to be newsworthy.”

McGowan has a voice and has lots to say. Her book isn’t an exposé but an excoriating criticism of Hollywood, and its messages, especially about women’s perceived worth. She wants to be part of seismic change. “It doesn’t mean it’s always going to be easy for people to change, but I just want people to be better by 10%,” she says. “And I think this has all raised our consciousness by about 10%.” She smiles. “I know that I’m on the right course.”

Brave by Rose McGowan is published by HarperCollins at £20. McGowan is in conversation with Laurie Penny at the Hay festival on Saturday 2 June at 1pm