Good for you. It's good to remove toxic people from your life. I know the sort of person you are talking about here: they just aren't happy, no matter what. And, they have a strange way making you feel like it's either your problem, or your fault, or both. No reason to keep in touch with this past co-worker.

One BIG THING here: let this person own their own choices. They choose what everything means to them, just as you do. The fact that somebody else continues to make bad choices should in no way effect the way you feel about yourself.