Why does Alice end her relationship with Dominic in the novel, What Alice Forgot?

Dominick is the school principal and Alice’s boyfriend. Alice has no memory of dating him. She’s initially a little cold towards him, but over time she warms up and realizes that he’s a good person. When her memories come back, she instinctively goes to Dominick over Nick. As time goes on though, she drifts further from Dominick and realizes she has too much of a past with Nick to ever give up on him.