why ?

*These is all my theories and may not be what the writers of the movie intended*

Adinah (or the woman playing the character "Adinah" on stage - we don't know) is coming to terms with her own womanhood and sexuality. As she was growing up, she had a lot of confusion since, according to her monologue, she was around mostly white girls or slightly-older black women and had a father who told her 2 words that becomes the motto she screams when she is tormented: "F--K 'EM!". It ties into the theme of each character realizing who they are and breaking away from what others expect them to be or doing the opposite - being exactly like what people want them - to be "part of the group".

Jeff (the guy who raped Choco) is showing his dominance to all the other guys, since he is the alpha male of the entire pack, and he thinks Choco is the weak one. As others have said, it is ironic since he is a homophobe (the locker scene with Tyler and the gay guy) - but he can have homosexual feelings like Tyler has but is less open and his drunken mindset is his cover. Again, it is part of the theme from above.

Fabian and Jessica never spoke again - it was a one-night stand so it's kind of obvious. Fabian (or someone else from his group) commented about how the girls from the slums were "easy", so he thought that Jessica would easily give (after working his charm, of course). At the very end, the only other reference to them is Jessica throwing up some time after - something each character did (Adinah talks about it, I believe) when they came to grip their reality.

It's a lot of ground to cover, but this is definitely the film to show the drama/psychology/indie fans.