Nick Cassavetes is not known for kitting out the directing side of his resume with traditional-sounding film fare – this is the filmmaker who gave us such features as the gritty "Alpha Dog" and the wrenching "My Sister’s Keeper," and even his "The Notebook" broke the mold when it came to Nicholas Sparks features, just by making it actually good – so it certainly seems bizarre that the guy who made "John Q" is now churning out a rom-com starring Cameron Diaz. But, despite its frothy appearance and basic plot, Cassavetes’ “The Other Woman” eschews plenty of standard genre expectations to make an unexpectedly friendship-friendly film about how terrible relationships can be ... and it almost takes it over the finish line.

The film sure starts off like any another romantic comedy: career lady Carly (Diaz) breezily falls into a romance with the dashing Mark (Jaime Lannister himself, Nikolaj Coster-Waldau), and the film’s opening scenes zip through their seemingly perfect new relationship, all set against the backdrop of a dreamy, movie-styled New York City. There are flowers! And dinner dates! And lots of sex! Ain’t love grand? But the joke is obvious and early – Mark is married, and when he leaves the sexy Carly in the city, he doesn’t return to a lonely home in Connecticut, but he instead finds himself at a sparkling McMansion populated by a giant dog and, oh yeah, his wife.

As Mark’s clueless wife Kate, Leslie Mann is at her ditzy and dizzy best. Kate is sweet and good-natured and more than a bit over-the-top, an obvious contrast to the coolly confident Carly. Kate has zero idea what her husband is up to – and, as it later turns out, Mark is up to plenty of double-crossing in both his personal and professional lives – so when Carly shows up one night to surprise her “boyfriend,” Kate is blindsided. Carly is also shocked, though her by-the-book nature means that she cuts Mark off immediately and completely. Carly refuses to be a homewrecker, which is both refreshing and also upsetting that such a simple moral center needs to feel refreshing, as audiences will likely be expecting to see yet another film where good women battle it out over a bad man. This quick choice is immediately thrown for a loop when Kate shows up at her office, all tears and questions.

The pair eventually decide to work together (not against each other, not in competition) to ruin Mark’s life. The idea itself is fun and frisky, but Melissa Stack’s script seems unaware of how much actual entertainment the concept lends itself to, as the film’s narrative structure is woefully designed. It takes far too long to get to Carly and Kate’s hijinks and big schemes, and instead of kicking right into them once they realize they are better and stronger together than they are apart, the script is littered with tangents and subplots. (And that’s to say nothing of their eventual discovery that Mark has yet another girlfriend, played by Kate Upton, who attempts to make up for lack of acting chops with a game attitude, and who they then need to bring into the fold, which gets repetitive.)

Yet, the film does pay attention to another unexpected element – the importance of the friendship that blossoms between Carly and Kate (and later, to some extent, with Upton’s Amber). Although the women are clearly very different, and have been brought together by some pretty heinous circumstances, the film eventually finds its footing by focusing on their bond and how it changes them in surprising ways. It certainly doesn’t hurt that Diaz and Mann display a canny comedic chemistry, and their best, boldest, and wackiest moments see the pair playing off each other with plenty of unexpected physical humor.

But despite the film’s insistence on portraying how important interpersonal female friendships can be, it doesn’t quite have the conviction to make that its sole focus. The film’s second act falls prey to a shoehorned-in romantic subplot that feels both very forced and very stupid, and it dilutes the charming and fresh messaging of the rest of the film. Instead of trusting that the main draw of a female-friendly film can be, well, its actual females, “The Other Woman” turns to played-out tropes and traditional plot movements that are easy enough to find elsewhere. Still, the film has real “girls night out” appeal, and even if it doesn’t believe in its own internal friendships, here’s hoping that its audience can recognize and value how wonderful it is to see even a spark of that on the big screen – and to ask for much more of it in other outings.

SCORE: 6.1 / 10