Well done on coming to the realisation that your previous behaviour was wrong. It speaks well for you that you want to make amends.

A couple of things for you to think about:

 - She most probably hasn't though of you in years, but it is just possible that her experience of you changed the way she interacted with other people in her life. She might not be happy about that and she might unload a world of recrimination on you. How would you feel in that situation?
 - Words are cheap, what might you do to show that your regret is sincere? You already mentioned karma, is there anything in your life you can point to which demonstrates the works and deeds you have carried out to build *good* karma? if there isn't, can you tell her what you are going to do going forward? Can you commit to volunteering with a charity like [Big Brothers Big Sisters][1] or something similar?

In short, what can you do to prove to her that this isn't just about making you feel better?

  [1]: http://www.bbbsi.org/