My mom is suffering from dementia and likes to put the blames on my sister in law. She always claims that she lost her stuff like pants, clothes, handbags and even money. And, my sister in law is always her suspect. it is even getting worse that she scolded my sister in law face to face in front of the kids at home. To the extreme, she even spread it outside of the family. My sister in law is extremely upset. How can we handle this? When it happens, my mom will curse and say she wants to kill my sister in law.
Google "Teepa Snow" and watch her videos on how to talk to dementia patients about things like "stealing".
Have your sister in law watch too. I hope the rest of your family is supportive of SIL and assures her, her kids and outsiders that it is understood that this is the dementia talking.
I'm so sorry to hear about what is happening with your mom. It's so tough. And your poor sister in law, I'm sure she is doing the best she can but it can't be easy. Like Barb said I would try and go back to the doctor and see if they can adjust her meds. Or maybe its time to discuss memory care.
I feel for your sister in law. I hope someone can give her some respite. And all the acknowledgement and validation she needs to know that this has nothing to do with her and all the disease.
https://www.agingcare.com/articles/how-to-handle-alzheimers-disease-lying-144204.htm
On a side note, have Mom checked for an Urinary Tract Infection as that can mimic other phases of dementia.
I am working in overseas and I can feel the tension and stress at home are max when I make a short trip home. I am kind of the middle man in between them. I am very stressful especially when I receive text or call from home.
Other than "stealing", mom always bring up some sad old stories about her marriage with my father. And again, she wants to kill my father, the mistress and then commit suicide, or want to run away from home. We try to ignore and redirect her attention to something else, but she will come back to the same topic after few minutes.
It's really tough. :(