If you did happen to bully someone when you were younger (I've done it before,though it wasn't really bullying, just being an overall terrible and aggressive person that attacks when given a chance, and I regret it greatly), if given an opportunity to apologize, you should at all costs. I would literally kill to be able to give a genuine apology to the people I've hurt if I was in the wrong. Rather than getting defensive, you should show people that you've matured. She clearly hasn't changed in the slightest. Yikes.