Mother in Law

I have a mother in Law who complains about everything, but behind my back. My husband is sick of hearing her constant bitching. He's told her, but it's in one ear and out the other. She is afraid to confont me because I might say something back. I've tried so many times to talk to her like an adult, but it's just not possible. She always says she is being treated like a 2 yr old. NO, but she sure acts like one.

Now she is upset because I went to the store real quick for some baby food and didn't bring her list.