The name "Alma" means kind and loving, and "kind and loving" describes Alma Del Mar perfectly. She's darling. Devoted. And she's also more than a little devastated—the film barely establishes her marriage with Ennis before Alma witnesses him locking lips with Jack, shattering her sense of security.
But above all else, Alma's diligent—she works long hours in a grocery store in order to help support her family. She's a hard worker, who picks up the slack when Ennis works fewer hours and brings in less money because he's leaving work to have his affair.
Alma quietly suffers for years, crying by herself when Ennis leaves the house with Jack. Alma and Ennis have one thing in common—the ability to keep their emotions locked up for a really long time. But like Ennis, Alma eventually snaps, divorcing him. And although it takes years, she eventually spills her feelings to Ennis. Brokeback Mountain is a quiet movie. Cowboys aren't known for being loquacious.
So it's Alma who delivers the movie's longest speech:
ALMA: You know, I used to wonder how come you never brought any trouts home. You always said you caught plenty, and you know how me and the girls like fish. So one night I got your creel case open night before you went on one of your little trips—price tag still on it after five years—and I tied a note to the end of the line. It said, "Hello, Ennis, bring some fish home. Love, Alma." And then you come back lookin' all perky and said you'd caught a bunch of brownies and you ate them up. Do you remember? I looked in that case first chance I got and there was my note still tied there. That line hadn't touched water in its life.
That's a lot of words, and they come out of hurt and anger. And there's an added edge to her accusations, because in Alma's mind, Ennis's doing something "unnatural" by having an affair with a man. Alma calls Jack "Jack Nasty, " which isn't very clever—does the phrase "Jack Nasty" mean anything?— but it's also not something Alma would say if Ennis were having an affair with a woman. Alma's attitude confirms Ennis's fears that he's doing something unnatural and may be punished for it.
Of course he's not doing anything unnatural, but he is doing something immoral: the character of Alma is around to remind us that Ennis is cheating on his loving wife, and he's skipping out on work to make that happen. That's a jerk move. Of course, the real villain here isn't Ennis—it's the homophobic society that prompted Ennis to bottle up his sexuality and get engaged to a woman in the first place—but still, Ennis is being an unfaithful scumbag.
But Alma, it seems, has the last laugh. Even though we never see Alma again after her Thanksgiving day "Jack Nasty" speech, Alma ends up…happy. Her second marriage seems awesome, and she has more kiddos. She has a stable and warm home life, which is pretty much all she ever wanted.
And Alma (who's as loving as her name suggests) totally deserves it.