Just some thoughts *spoilers*
This is just my theory. Please let me know what you think.
A. Emma.
Flashes show that Diana liked the name Emma, and that she had an abortion. I think Emma popped up in her future life fantasies for a couple reasons.
1. The day of the shooting, they walked past the pro-life crosses, and she was reminded of the painful choice she had to make, and she saw the cross that had the name Emma on it.
2. Emma told Diana- "You hate me." and Diana was obviously hurt by this remark. I believe this was Diana's internal struggle, with having to make such a traumatic choice. I think she felt she made the right choice to abort dirt bag's fetus, still there was a part of her that was dealing with a lot of confusion.
3. When Emma was watching the movie with guns, she told her mom "It is funny like a joke." Diana told Maureen she didn't report that kid to anyone for making the gun threat because she thought he was joking around. Emma also said "You are scared mom. Don't be so scared." I think that was just a way for Diana to relax, and just accept death, and not to fear it"
4. Diana and Maureen talked about visions, and how Maureen saw god. Diana said "What if you don't see it?" I wonder if Emma was the vision she needed to see?
B. The husband- We all know that she was seeing the professor before she died. Or she at least hooked up with him. In the fantasy life, she thought he was cheating on her. In real life, she talks about how she keeps getting his voice mail. I am guessing that he was a married professor, and she was the other woman. Which is why she was so concerned about the cheating.
C. The kid with the gun- His face went from "I am on a killing spree *beep* all y'all" to remorse after he shot Diana. He looked as if he felt bad for what he did after seeing Maureen's reaction. Do you think he felt sorry for his actions?
D. Maureen and her comments about Diana getting upset over the word Slut. I think Maureen had that misconstrued. I think Diana thought it was an ugly word to call females, and the guy she kicked in the crotch called her that. The guy she dated, and had to have an abortion. When he was on the phone in his truck, you hear him tell his friend "Oh it was nothing, just some slut." I think she was thinking of the girl that used to be Samantha (the skeleton). She knew the pain of being called names like that, and it made her upset that the guy who wrote slut on the blackboard was disrespecting the remains of a teenage girl. I also think she felt bad, because the teacher was so sincere when he said he enjoyed teaching them, and that had to happen.
Yeah I over analyzed this movie.