Is my ex-daughter in law being unreasonable or is it me?

My son and his ex are in the process of a divorce. The ex already has a new boyfriend she's living with and my granddaughter lives there with them. Now that my son has a new girlfriend (who is 10x better than his ex was), the ex says she has the right to withhold visitation if the new girlfriend is around. The new girlfriend has never posed any threat to the child, and as a matter of fact, loves the child very much and spends more quality time with her than her own mother does. Since the ex has full custody, does she have the right to make these sorts of stipulations? She says that I don't respect her wishes if I let the girlfriend around the child and that the court can stop my rights to see the baby if I don't respect her wishes. I think she's full of feces, myself.