“Lola Versus” star Greta Gerwig says she was more concerned about making her character authentic than making her likable.

A woman on the brink of turning 30 gets dumped three weeks before her wedding. We all know how this movie will play out: She’ll hit the bars with her two girlfriends and sassy gay pal, where she’ll drink too much and moon over her ex. Ben and Jerry will have cameos. It’ll turn out that another guy was the Right One after all.

Not so in “Lola Versus,” out Friday, which stars Greta Gerwig as the title character. “I think the movie is more related to reality than a lot of romcoms are,” she says. “It bucks the cliches of, ‘There is a Prince Charming, and it’s all going to work out in the end.’ It does [work out], but not in the way you think it’s going to.”

The film takes a swipe at the oftentimes treacly genre by making Lola, well, kind of insufferable — and not in the “she’s pretty, but she’s a klutz!” way that lead roles in these movies typically are written. “She’s not adorably a mess,” says Gerwig. “She’s actually a mess. The character isn’t paying lip service to trauma — it’s actually showing her going through something and then making the worst possible decisions. There’s something to how big her screwups are and how badly she screws up relationships.”

Lola can be grating and horrible — an unusual choice for a character that has to carry a movie and is in virtually every scene. “I tried not to worry about if she’s going to be likable, if she’s too annoying,” Gerwig says. “What is really likable is what’s truthful, and that’s the ultimate thing that will win people over. It’s not a flattering portrait; it’s just realistic.”

Having to carry the movie intimidated Gerwig (“Greenberg,” “No Strings Attached”), but she coped by being as negative as possible. “I always write reviews in my head before I start shooting, just thinking of the terrible things people can say. The thing is, I love acting and I love making movies, and as soon as I start acting I’m not worried about it — I’m just having a good time. It’s more of the buildup and anticipation that makes you worry.”

Hopeful thinking isn’t part of her preparation. “I never write positive reviews in my head,” she says. “I just prepare for disaster.”

Landmark E Street Cinema, 555 11th St. NW; opens Fri., $8-$11; 202-452-7672. (Metro Center)