First off I am so sorry 🙁
I honestly think you should just start by talking to her about it. Be as honest as you can, tell her what you did, how it makes you feel, ask her why she did what she did, get anything and everything off your chest that you need to. Then let her explain herself, and go from there. It’s going to be hard, but at least it will be resolved and you both can move on no matter what you two decide to do about it.