My ex girlfriend is dating someone else
If she really believes you are the best thing that has happened to her then what is she doing sleeping with someone else? Don't play games, just have nothing to do with her.
It will not be easy as you have a history and invested feelings.
Her actions tell a very different story then what s coming out of her mouth.
They have to want to fix themselves and seek the help. IF so, do you really think, if she was to return to you, that she will not do this to you again if she is feeling depressed?
If you feel she has crossed the line then you should do what you know is best, leave her alone.
One day at a time and you will get stronger, but you must see this for what it really is in order to have the conviction to keep your resolve. I just know she has changed a lot recently she is depressed and trying to do things to make herself feel better, even if it means hurting me disregarding how I might feel. If she is depressed then she should seek help or try to better herself emotionally.
It still doesn't give her the right to hurt you in the process.