His ex?

So I've been talking to a guy (cue grinning like a 12 year old girl) 🙈 and I really like him, we talk all the time and he's just the sweetest. I found out he had a on and off relationship with a girl for 3 years but he ended it because she treated him so badly and tried to get him on drugs (she was on some pretty bad ones) but he finally realized that through sticking by her, he deserved better. Anyway cue insecurities. What if she turns her life around (which I hope she does because I'm sure without drugs she's a nice girl) and he realizes this? Then goes back to her?