First step is urinary testing, as has been said, if this is new. Then it is time to get more testing, including neuro testing. If this is sudden it can be due to a number of medical conditions.
If you can get her in to her doctor, she should be checked for a UTI. If you think she has a fever I'd take her in tonight. If she's not had a cognitive exam, I'd have them do that too. Anger is very common in people her age. Depending on the outcome of the exam, she may be a candidate for mood medications. Hopefully he is durable PoA for her. If you get her to the doc, also request a Medical Information Release form and have MIL fill it out and designate her son (or you) as authorized to get and receive info from her doctor. Without this they legally cant share her info with you no matter what. I hope this info helps you!
Thank you for replying. My other problem with her getting angry is she will not let me clean her. She even refuses do it herself. This is all taken place in a matter of a week. Will contact dr. Everyone has been helpful
Sudden changes in personality is an indication of infection in a senior.
I would take her to an urgent care tonight.