My mother in law lived with my husband when we got married and for the first few years everything was great! We all worked together to pay bills and keep the house clean. Then, she spent the summer of 2020 with her daughter in another state. After she came back, she was completely different. Refuses to help out around the house at all. Says she doesn't feel like she should have to pay any bills. When we talk to her about it she is apologetic and says she will do better and didn't realize it bothered us so much. But then she never changes her behavior. She keeps acting the same way as she did before we talked to her. We are worried that she may be developing dementia or a mental health disorder. We want to have her evaluated but we just don't know how to go about it. Any advice?
Hopefully she is under some medical care. Start there with making an appointment for an evaluation. It can be explained as a routine checkup.
Ask your husband to have a nice chat with his sister to see what nonsense she may have filled mother's head up with while visiting. And ask when he can drop her off there again permanently.
Unless you see other obvious signs of dementia in your MIL like putting her car keys in the refrigerator or not knowing the day of the week, or repeating herself incessantly, I wouldn't worry about dementia but having someone whispering in her ear instead.
If you see other signs of dementia, her PCP should be contacted for a physical including a mini cognizance test.
Good luck 😁
If not, I'd start with her PCP and see what referrals they suggest.
Good luck.