How do you ladies feel about someone else showering with your child?

Ok maybe the topic sounds weird BUT my mother in law takes a bath with my daughter she's 3 and I hate it! But I have nooo control over it half the time I'm at work and I just think it's Nasty to share water with a child. Especially not ur child. How do I tell her to stop without offending her? My boyfriend has no problem with it. And my mother in law has MS not like it makes a difference but I know she won't be around that long. How do u guys feel about it?