Like you said she has changed.

Love her for who she is, not what she was. The past is the past and we all have things in our past that we would like to forget. Be happy that she improved herself so much.

Either find a way to deal with her past, not to sound harsh, by trying to just let go or talking to a therapist with or without her, or move on. If you can't get past it, things will get even worse for you and her if you stick around.