Wow, never knew about this thread. Great question.
Let's see, what's been mentioned already:
1. someone quoted the shortstory...the electric current between the cowboys, vibrating floor board, the excitement to get out of there, and staying out all night...Alma sure knew, if she didn't already, that more than just a kiss was going on between those two. She could probably feel the heat and electricity from way over there.
2. great insights from mpj and asali, that Alma wanted to observe Jack and Ennis and see more of the interaction between them, not just the electric sparks.
3. Alma wants to understand this man who has such impact on her husband, to find out more
4. Simple hospitality and courtesy. It was kinda rude of Jack to come calling and not visit for a while. In fact, he knew Ennis was married so it was rude not to bring something on his first visit. To stand out there and not come in the next morning was even more rude.
5. Alma was really trying to make the marriage work. She said to get a sitter so they can go out for a nice dinner. Ennis shut her down from the get go, and never gave her a chance. He kept his Brokeback Mountain separate from his "stuck life in Riverton".
Texans don't drink coffee...Alma finally had enough of this rudeness and ready to give him a piece of her mind. Then Jr came in asking for a big fish, and she could say nothing, except with tears. Ennis saw 'em tears, but the separate part of his heart was pulling him out the door. He could do nothing about it. Got no reins on this one ladies. See you on Sunday. That's was a heart-wrenching scene.