I suggest you walk out on her when she treats you badly. If you don't live together, and you're at her house, walk out immediately. Or if she's at your house, tell her that her behaviour is unacceptable and she should leave and not return until she can be civil.
In short, people will treat you in the manner you accept. You have to show her that you won't accept this behaviour.
If you do live together, it will be far more complicated. I hope you don't!
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.