Does the provider have any type of schedule? Such as maybe a time period when all the children are indoors napping or playing in a structured activity?
If so, maybe you could schedule your important meetings during that quiet time?
I also agree with the previous poster that mentioned ratios. I imagine a group of kids are pretty loud when you aren't the provider or the one actively engaged in caring for them but it seems to be that unless she has more than 10 kids it shouldn't really be the circus you are mentioning.
Does the provider have regular hours or is she open 24 hours a day? A mean spirited part of me thought, well you could always be super loud when the kids are all gone home and she's enjoying her quiet time.
Although that would solve nothing at all and would probably only further add to the issue but I totally understand how you are feeling. I operate a child care in a neighborhood with houses close together and I try hard to make sure my kiddos arent disruptive to the neighbors.
Im sorry you are in this situation. It's a tough environment we are living in right now.