By alone, do you mean she leaves the house or she is in another room?

If you have court papers saying that the mother is required to have supervised visits AND that the supervisor is supposed to be the grandmother AND if the grandmother goes outside the home and leaves the mother alone - I would call the police, show them your paperwork, tell them the kids are in danger when the grandmother is not there and have them do a well child check. They won't do anything other than check the welfare of the child and see who is supervising (unless the mother is really messed up on drugs at the time and they may take the child). But you will get a police report saying the supervisor was not there, the mother was alone with the child, and that you can take back to court. But becareful because sometimes the court will enforce the order and sometimes the court will make the visits non-supervised so that there isn't any issue anymore. It all depends on which judge you get.

If the grandmother is just going in another room or she is going outside while they stay inside. I don't know what you can do. Maybe take the child to counseling or child protective services so that someone else can find out whats going on during these visits.

Either way you have a long road ahead of you and I wish you all the best. Keep us posted

So glad to hear you are going to do everything to protect this little baby. It isn't fair and it hurts financially everyone. Our prayers are with you on this. Please keep us posted. You are a good and kind women to love this child who you didn't birth as your own. I truely admire you. Biology is over rated. Anyone can produce a baby. The true mother gives the love, and sacrifies. May god go with you in this. We are all praying for this little angel.