I think the scene with her mother was just her extreme loneliness. She just wanted affection from someone, anyone, but because she has some screws loose that was difficult to find....
I think there's also aggression in that encounter with her mother, because E. is breaching the boundary in one massive way (incest is taboo in almost every culture) and one big-ish ways (even industrialized nations are still iffy about same-sex couplings). Note that I'm not saying she was attracted to, or was trying to have sex with, her mother; rather, she used a symbolically laden way of expressing her aggression -- more evocative than, say, breaking dishes or slapping her mother.
"All you need to start an asylum is an empty room and the right kind of people."
I think all 3 responses are right on. When she says, "I saw the hairs on your sex," it's a withering put-down and at the same time an expression of complete intimacy and connectedness.