What to do about a meddling parent at my daughter's school?

she sounds like she is very unhappy in her life and belittles others to make herself feel better. I had a similar person in my life and decided I would be extremely happy when she was around - all smiles, only positive comments. It made it hard for her to then change the mood and comment about my children. when she did try i turned the conversation around very quickly, with an "oh, well..hey how about this weather?" (or something).