Most Helpful Guy
Personally, if I was you. Feeling like this, I would legit go to her house and speak with her. Not some begging type sht though. Just a 1 on 1 and just throw everything out, expose yourself for the man you once were and confess of how much of a douchbag you were, flirting and doing these things behind her back. Speak from what you feel about the stupid sht you did to make her leave you in the first place.
Then, and only then will she possibly realize that you understood the gravity of this problem and you fully are aware that you'd never do it again.