As I previously discussed on a classmate post, Nick has been manipulating Amy from the beginning of their marriage. He wanted Amy to be someone who she was not (even though that is how she presented herself at the beginning for their relationship), as you stated, Nick dragged Amy to Missouri to save his mother, but unfortunately it was too late; lastly, Nick ‘convinces’ Amy to use the last of her trust fund to open his bar. Moreover, Nick had control of Amy by her insecurities, which she outlines her complains in one of her monologues,
“…Being the cool girl means I am hot, brilliant, funny woman, who adores football, poker, dirty jokes, and pburping, who plays video games, drinks cheap beer, loved threesomes and anal sex,