Tbh, I would just say to your husband how you feel, make a note of things as guys tend to say that girls exaggerate etc so I would basicly call him out on it, let him know how you really feel and also I would say to the mother, I understand that you dont want to rock the boat but at the end of the day, if she is annoying you then you have to face it.
I am one of those say it how it is so sorry if it seems blunt but whenever my MIL annoys me (obviously not to your extent) I just say back off basicly and she does. She may not know that she is doing wrong as no one is saying to her..