It's not. It's because your Sim had a bad relationship with her parents as a child, and now she doesn't like to see those family members whom she had a bad relationship with. It doesn't have anything to do with any of the Childhood phases, it's to do with the relationships you have listed in your Sim's panel with family members after she ages up to YA. I made a thread about this a while ago: http://forums.thesims.com/en_US/discussion/923734/ugh-family-moodlet#latest
So you can't get rid of it by removing any traits because it isn't caused by traits. I think that the only way to get rid of it is to get rid of the entire relationship... which, I think, you'll need MCCC for.