One trait with my ex that is very dicernable is the extreme distance she puts between us when she does meet someone she likes. She becomes more critical and condescending in her tone. it almost reeks of bitterness and resentment. I never know from one call to the next which attitude I will get.
Sounds about right. She basically considers her options as a single person and wonders, "what if", about you. Not exactly inspiring you to a lot of confidence in her motivation even if she wanted to try again. You'll probably get a similar call when things with BF end. Hopefully at some point you realize that you don't have to be anyone's fallback plan. That's all beside the point since she's now interested in someone else...while unfortunately it sounds like she's content to let the R with her son slide.
As for you, it may help you to think of her as any other woman. Is her behavior attractive to you? Her being selfish is pretty much who she, at least right now. She'd need work to be anything else. Would you click on her profile on a dating site if it said, "extraordinarily selfish person".
You cannot be lonely if you like the person you're alone with. Dr. Wayne Dyer