I worked with one of the sweetest, nicest ladies you would ever want to meet and it seemed like over night she became nasty, rude, short tempered. After I talked with her son and daughter (I was close enough with her to do it) they took her in for an evaluation...Alzheimers. My step mother, not always the most clued in socially but still tried to keep her tongue has taken to being rude and when you call her on it she is honestly confused because she feels that, say, telling her new DIL that she is fat and needs to lose weight is ok. She is in the beginnings of dementia. If your mom was normally not like that, it would not hurt to have her evaluated. There is some great treatments now that can slow down the effects and smooth out the bothersome behaviors. And it is shocking to those close to the person showing these behaviors but remember, it is not the person, but a disease (be it dementia, alzheimers, vitamin deficiencies, simple dehydration, diabetes, thyroids ect) causing it.