Grow bags

I’ve recently had a little girl who sleeps in a grow bag, but her nanna constantly tells me it’s too cold and tries to add extra blankets, and tells me that’s wrong to make her sleep in a sleeping bag as I wouldn’t like it. But I’ve tried to explain that she gets really warm in the night as our room is always warm. And she doesn’t need extra blankets, I understand her worrying in case she gets cold but surely she wouldn’t be sleeping all night long if she was cold?