Amy's father didn't love her so she grew up not loving herself. That's why she looks for men who will hurt her ( a reiteration of the father-daughter relationship). When they prove they don't love her, instead of going away, she stays. Not only did her father not love her, humiliate and terrorize her, but she also had a perfect five year relationship with a boy who raped her.
Frank grew up in the middle of a divorce and as an adult he probably hates his mother. I guess this is where all the lack of respect and hatred towards women comes from. In psychotherapy, psychopathic men like him ( huge levels of self appreciation, absence of guilt, absence of empathy, promiscuous tendencies, aggressiveness) are called "predators", they seduce through a "passive-aggressive" method which Frank applied successfully in Amy's case.
One night they casually met in the club. It was enough for her to see him to feel that thing called "happiness". They were both so high that they kept spilling their drinks, "you're a very special girl" he said. They went home, she put on "Witchcraft" and did the striptease for him. He laid on the couch with a skitzo look, stoned, unable to react to the clothes she would throw on him. She felt as if, while taking her clothes off, she were actually tearing her flesh off , offering him her soul.
She spilled pear juice on herself and he started eating her with a hunger which was synonymous to despair. She strapped his shirt and they fucked. When they stopped they started talking and things got pretty tense. He was angry and wanted to be left alone, she wanted to get into his soul no matter what.
He slapped her and she began to cry. Instead of hugging her, he continued to bark, accusing her of being weak. She shouted she was not his property. And then she went down on him and he became weak. She was on top, he held her so tight against his chest, it was the perfect expression and exorcism of despair and mal d'etre, the absolute abandonment. And she loved the whole soap opera.
After her father died, Amy met a boy who was just like him. Mentally disturbed as well, he fucked her brains pretty well. Abandoned by her best friend and living in a place where she did not know anyone, Amy became borderline. To this day she feels that the only solid reason which keeps her from suicide when the absence of meaning in her life is much too obvious is represented by her mother who doesn't deserve to suffer even more than she already has.
Frank is 32 and has smashed five cars so far. His body is full of scars. When she kisses his caramel skin, the scars melt into her mouth like tears.When they have sex she likes it when he strangles her and I believe there is a chance for things to go crazy... Just like there is a possibility for her to do a completely irrational thing out of the despair of being abandoned.