GRRRR!

I am really angry right now so maybe I should have waited before writing this. I am the nanny for a 4 year old boy and he and I get along very well. I will probably ask for a raise in the future but I am satisfied so far with what I am making. Here is what has me angry: I have had 2 friends call me and tell me about my MB complaining about me on the web!!! She does it on a neighborhood FB for mothers which I am not a member of but I have friends and other part time bosses who are. My friend let me go on there and see, MB does not mention me by name but mentions 3 incidents, one where I served  my charge and 2 of his friends a macaroni and cheese casserole MB was planning to serve for supper. Another one where she thought I was serving him Gatorade, which I was drinking and he had watered down OJ. And some other thing I forget at the moment. She never tells me these concerns, she is always very polite to me, but now I find she is badmouthing me behind my back. Do I confront her? Let it go and say something vague?