At its rotten heart, Bachelorette is a gender-reversed The Hangover. Shenanigans happen on the eve of a big wedding with the bride standing to lose everything. Here, it's an accident that leaves the bride's wedding gown torn up and soiled the night before the big wedding. It's the bridesmaids who must put things right even as they stumble about in their worst behaviour on one drug and booze-filled misadventure after another.
But even as a gender-reversed Hangover, vistas of comic possibility do open up. While the buddies in The Hangover series misbehave in Las Vegas and Bangkok, they are also on their best behaviour not to alienate the annoying, eccentric, and socially-inept goofball played by Zach Galiafianakis. But since we're dealing with bridesmaids under Hollywood's gender model, it's okay to have them exude different kinds of mean attitude to each other. The Bride is a fat pig. Her bridesmaids consist of a controlling alpha bitch, a bitter misanthrope who's also into misandry, and a clueless bimbo. We gather they're all best friends because each member of their happy group can find something to condescend or feel superior to in everyone else.
As long as the script pulls no punches and keeps crossing the line on civility, it's actually fun to watch the cast of characters show open contempt to each other while desperately sticking together to rescue the wedding dress of the bride, whom they all despise more than each other. Largely based on the original play by Leslye Headland, Bachelorette is pungent, uncompromising, and hilarious except when it succumbs to sentimentality and preachiness in its inevitable, soul-redeeming third act.