I can understand how terrible you must feel having to put up with that everyday. Take into account that you don't know what is going with her at home that could be causing this highly critical thing she is going through. That doesn't make it any easier on you but maybe can relieve a little of the feeling to blame. Is she only critical with you or is it everyone? Makes a big difference. She could be suffering from a mental illness. I try to be sensitive to that since I have a mental illness that affects my work day.

Just throwing out ideas. Good luck and hope things get better.