I'm sorry you have to go through this

For me this is a betrayal, regardless of how it's framed. I would mourn the relationship as if it's over. I wouldn't break up necessarily, but I would try to move on, just like she's doing.

Give her all the space. Right now she feels secure, because she kind of feels she has you to fall back on. Don't contact her first anymore. Spend more time with friends and family. Be open to new relationships. When she sees that you have a life without her, she may think more highly of you and she may regret her decision. Right now she's taking you for granted and you should prove to her and yourself that you will survive and thrive no matter what. Treat yourself with respect, even if she won't. Get in shape if you aren't already. Now is the time to work on yourself. Don't wait for her to make up her mind - you need to feel ok even if she's got be for good.

If she decides to come back, consider long and hard, if you will be able to trust her again.