It's a chick flick, I'm a feminist and I'm not ashamed: the new film Bridesmaids, released next week, is brilliant. I have weathered disdainful looks and the painful experience of both my sisters disagreeing with me at the same time (they are like coordinates; separately they might not tell you much, but when they intersect, that tells you a lot). They said it looked rubbish: they haven't actually seen it, just the trailers.

My school friend said: "It's about getting married. Women, desperate to get married. What kind of a feminist are you?" I cannot deny any of this: the posters are right there on the sides of buses, five women, dressed in pink satin, propping up the glorious life-defining triumph of matrimony.

Nevertheless, this is the first film that has been made in my lifetime in which a woman is given a funny line. Since glorious Technicolor, pretty much, the idea of a woman with wit has been cinematic sacrilege. It's just so strange: the popularity of cinema exploded in some part due to screwball comedies, which were gender-blind in their joke distribution.

Between His Girl Friday and now, something went terribly wrong. There is an outside chance, in a film, that the heroine might be kooky or her best friend might make funny faces. In French films, you might find a woman with a ready laugh, but never one who is the source of the laugh. Sometimes women are arch and that might raise a smirk of admiration. But jokes? Not a chance. What if she accidentally said something funnier than Ben Stiller or Simon Pegg? Imagine how unsexy that would be.

So I don't care that Bridesmaids features bridesmaids, nor that it is ultimately uncritical of the American nuptial hyper-consumption that, from a distance, looks like a disorder. They could make a film which came down broadly in favour of female genital mutilation and it would still, if the women had lines like this, be more feminist than Thelma and Louise.

I went to a screening for real-life brides, women who I cannot describe as my kind of women – really nice and all that, but fancy wanting to get married. At 27! They all loved it too. I don't know what this proves, exactly.

Carla, 32, said: "It was absolutely my sense of humour." Her friend (and real life bridesmaid) Jo, 33, said "Sex and the City had its place. It was independent women, who didn't need a man. But this is more like actual women, and the way we converse with each other."

The film was written by Kristen Wiig and Annie Mumolo, who have written for Saturday Night Live and are friends of very long standing. A couple of women at the screening said that you could tell that good friends had written it because they really understood how friends spoke to one another, but I think this is just a tendency to explain anything women do through the lens of experientialism, lest we get too big for our boots and use our imaginations.

Wiig plays chief bridesmaid to Maya Rudolph. Two other things that are startlingly unusual for Hollywood – the bride is not particularly thin (this sounds small but seems important) and the heroine has money problems. She literally lives in a shared flat, in her mid-thirties, with odd people (including an incongruous-looking Matt Lucas), worrying about money all the time.

Charley Beard, 30, who's been a bridesmaid (in real life) six times, said: "That's always how it is: you'll get a bridesmaid from every period of the bride's life, there's always one that's really successful, one that's had the kids, one that's struggling for money, there'll be a sister or a cousin who you have to be a bit careful around." But it's really unusual to see this reflected in a film.

Tension is a precondition of comedy; not everybody can be loaded and really pretty and really sweet. So maybe that's when women stopped being funny in films, when films decided that it was not cool for us to have imperfections, not even financial ones.

Two photographers, Caro, 27 and Lisa, 30, are both newly married: Lisa has a load of piercings. For this reason, I thought, of all the brides, she would be my kind of bride (I don't know why: it's not like I have any piercings). She liked it, but said: "It felt like girls doing boys humour." "How do you mean?" "Women aren't funny. There aren't any funny women comedians."

So there it is: if you think women aren't funny, this won't feel like a feminist gesture, this will feel like women pretending to be men (who are funny). And if you think women are funny, you will be astonished that you have waited this long to see them be funny on a big screen. But either way, you will laugh.