Image copyright Universal Image caption Moretz as the warm-hearted yet naive Frances in Greta

US actress Chloë Grace Moretz knows a thing or two about LGBT education.

Growing up in the conservative Christian town of Rome, Georgia, two of her brothers felt they had to "pray the gay away" before coming out.

That led to her taking a role in last year's Miseducation of Cameron Post, where she played a character who was sent to a gay conversion therapy centre.

Now, with stories about equality teaching hitting the headlines, Moretz tells the BBC that there should be "no age limit" for learning about these issues.

Speaking from Los Angeles ahead of the release of her new psychological thriller, Greta, the star says: "I think children know what you teach them.

"I had two gay brothers in my family, and our little cousins have known my brothers as gay from the time they were little bitty babies.

"They grew up understanding that was a part of life and that love comes in many forms. So I feel like there shouldn't be an age limit to that - I think it's unfair to the child."

She adds: "It's just like saying 'I'm not gonna give my kid the full colouring box because right now they should only draw with black and white' - we don't work that way.

"Why not give them the full range of the spectrum to grow into themselves and understand that they have the world in the palm of their hand."

Image copyright Universal Image caption Moretz on the "incredible" Isabelle Huppert as Greta (left): "She's so cool, she's so incredibly terrifying at the same time as being so elegant, and stunning - it's a crazy mix that only she could do."

Although she's only 22, Moretz has one of the most varied CVs in cinema - with a filmography that includes horror (Suspiria, Let Me In), action (Kick-Ass), comedy (Big Momma's House 2, 500 Days of Summer) and heartwarming kids' fare (Hugo, Muppets Most Wanted).

For her latest role, the actress plays Frances McCullen; a young out-of-town waitress who's trying to make it on her own in the big bad city.

Twisted fairytale

The girl, who has recently lost her mother, befriends an apparently dear old lady, Greta Hideg - played by the "incredible" Isabelle Huppert - after finding her handbag on the subway.

But it quickly transpires the bag was left there deliberately - and Frances is fated to become the latest in a long line of girls that Greta hopes will replace her own missing daughter.

"It's a twisted fairytale in a lot of ways and a lot of fun to jump into," says Moretz.

"What I found interesting when I first read the script was this psychological insight: Is a monster born or is a monster bred?

"It's a movie about grief and loss and isolation in a lot of ways and what that does with people's minds."

Would Moretz return the bag herself though, if the situation happened for real?

"At this point I can safely say I'll never be a good Samaritan ever again," she jokes, "I'm never gonna help anyone!"

Image copyright Getty Images Image caption I'd put that bag down if I were you...

The former child star admits she's "always been interested in the dark or the occult," from the time she did her first movie, 2005's The Amityville Horror.

"I've always had this kind of underlying darker tone in my career," she explains.

"I think it's just I've always been interested in the abnormal psychology of that and to portray that on film I think is really interesting and so multi-faceted and you can really dive deep and pick it apart and kind of wear this unnatural skin for yourself.

"As an actor, for me, I think it really broadens my emotional-scape."

The more frightening moments of her latest film involved a maniacal confrontation in a restaurant (she actually worked in a Dublin restaurant to prepare), a bloody scene involving kitchen utensils and - most terrifying of all - being locked in a cupboard.

"That was definitely the worst moment for me," she says.

"I've jumped out of aeroplanes and I'm completely fine with fear most of the time, but my one thing is claustrophobia and it's just completely debilitating.

"We tried to keep it as succinct as possible and the least amount of takes as we could possibly do but sometimes, how it goes, you don't always have that option.

"But [director] Neil [Jordan] was really wonderful with me, and really took his time with me to make sure that I felt as comfortable as possible... while having a panic attack!"

Male lens

With 15 years' on-screen experience, Moretz has witnessed the darker side of the film industry too - and recently pulled her support from the animated film Red Shoes and the Seven Dwarfs, to which she lent her voice, after a promotional poster appeared to body-shame Snow White.

While the actress says she's "seen change in the industry", she believes there's still a long way to go in the fight for gender equality.

"Representation is still few and far between," she says, "because, at the end of the day, most of the time we're still being directed, written, seen and shot through a male lens.

"They can cast a female lead but that doesn't mean it's a female-driven story, as you still need people behind the scenes to be of a different mind-state because that's how you see progress.

"It's not just the poster child - 'oh we have a female lead' - it's about what's actually happening in the inner workings and what the product is gonna be.

Image copyright Universal Image caption Maika Monroe as Erica Penn, Frances' roommate and rightly-concerned friend

"The most I can do as an actor is show up and do my job but there's a hundred other people who take what I do, edit it and shape it into what their vision is.

"So it's one step in the right direction for sure but we have a lot more ground to break."

The next stop on Moretz's own personal mission to out-spook all of her peers is providing the voice of the "iconic" Wednesday Addams in the new Addams Family animation.

Recording her role was "a total blast" but with a similarly "ominous umbrella hanging over it".

"I don't know what that says about my personality," she laughs - "or my psyche!"

Greta is in cinemas from Thursday

Follow us on Facebook, on Twitter @BBCNewsEnts, or on Instagram at bbcnewsents. If you have a story suggestion email entertainment.news@bbc.co.uk.