How would you feel if you couldn't meet the woman that's gonna be around your child?

Last month me and my BD's custody agreement changed. We have a 10 month old son and he recently served me a restraining order which we had to court about and he was granted the restraining order. So we are only allowed to communicate through a third party. When we do a drop off it has to be through this specific center so we have 0 communication with each other. My sister went on his Facebook and found out he's dating a girl and they are already living together! I do know OF this girl and they've known each other a few years but doesn't seem like theyve been dating long and if shes living there shes around my son. How would you feel about this? I'm only legally required to stay away from him but not HER. I think I should meet her. I have had no mentions if her and I'm the mother. I don't want anyone around my kid that I haven't met.