a fallback
A fallback is the person you only talk to when you have no one else to hang out with. They’re like the last piece of pizza when everyone else is gone.
You had no one else to talk to and went to your fallback because you didn’t know what else to do.
You had no one to go to the movies with, so you went to your fallback.
You were lonely and your fallback was the only one who talked to you.