Sharing toys

I’m a stay at home mom and I watch a 3 year old regularly and a 1 year old 3 days a week on top of my own 2 year old. She has to share me and her whole house, I feel like her room is off limits to the other kids and if she gets overwhelmed she is allowed to go into her room by her and play with her toys. I put all of her nice and new toys in her room all while having toys in the living room and play room. The 3 year old goes home telling her mom she isn’t allowed to play in my daughters room and her mom brought it up to me.

My question is, do you think it’s fair that my daughter can play with her toys by herself? She has ti share so much already and her room is the only place she doesn’t have to share. Obviously if my daughter has play date friends come over that’s different, but for kids who basically live here, I think that’s different.