Gave up...For What

I didn't get why Angie said Jules would hate her mom if she would stay with her father. And why would her mother (Rebbecca) fall apart if she could not have her daughter full time. In fact the whole conversation made no sense. It just seemed all wrong for why he would sacrifice turning over his daughter without a fight. I can understand shared custody but to settle for every other weekend even when his daughter wants more made no sense.