Kumari, I agree with you up until the time Alma sees them from the doorway. Then my own heart nearly broke because Alma isn't a bad person and doesn't deserve to get her feelings go through a ringer. Then again, nobody in the film deserves the pain they've experienced.
Michelle Williams is dead-on in this scene when she says, ever so quietly, "'Lo." That is the only greeting to Jack that she can muster. No one in the room is breathing, for different reasons, of course.
I feel for Alma, as another tragedy in this story.
But what makes the tension even more palpable is that she is a part of the society that rejects their love. Alma is a good person, but she is homophobic and she is repulsed by what she has seen. She looks at Jack as if he is a circus freak.
I won't speculate as to how she would feel if she were not in that unenviable position, but her venomous "Jack Nasty" comment gives us a pretty good idea.