Her life up until now has been one of sacrifice. She sacrificed for her Mom, her sister and everyone else she knew. Excpet herself. She doesn't like focusing on herself. Then she'll have to remember her past. And she doesn't want to. It makes her feel sad. She keeps men at a distance so she doesn't end up like her Mom.
Brad seems like a carefree surfer boy, someone she'd never like, let alone spend time with. And he makes her feel things. Things she refuses to feel. But he won't take no for an answer.