My MIL moved in with us (we have a detached living quarters to our home) and her daughter insists our 95 yr old mom has Dementia. Mom has lived with us 2 months and doctors, friends are amazed with this woman. She has to do a flight of stairs to get to apartment, shows no signs of dementia and is a joy. Gets up each day, fixes her coffee, do makeup, hair, dress etc. And she has what I call normal memory for being 95, great recall uses a cellphone even though it is frustrating, engages in conversations. She had some medical issues (a minor TIA from untreated high BP) so we've seen a neurologist and he said she follows directions and doesn't have dementia. She had not been taking her medications while living with daughter for her blood pressure and had been under a lot of stress. But we've been able to get her health back. There is a lot more about the situation but we're going to be going back to where the sister lives (110 miles away) to get moms house ready for sale soon. The siblings do not get along and I just am not good at figuring out what to say.
I would let your husband contact his sister with updates. I always bristled when my SIL was the go-between for my brother about our parents. I felt like it should be my brother's job, not my SIL. It annoyed me that my brother wasn't involved enough to contact me. That's just my 2 cents about it.
Good luck, it sounds like you've got it handled. Just have compassion for the sister - she may be battling demons you're not aware of. She may feel guilty that mom is doing well now and doesn't know how to maturely express those feelings, so just isolates herself.
My mom much preferred my SIL, was much more cheerful, compliant and happy when SIL was around. We used to joke about it, but it still hurt.
My SIL made it better by saying mom didn't have to put up with HER as a moody teenager, or cope with her childhood issues. My SIL also claimed until the day mom died that she didn't have dementia. She did. I had the neuropsych testing that said so, and I also knew that mom's reasoning was off, because ultimately, I knew her better.
If SIL doesn't want updates, just send an occasional text and don't expect a reply.
The daughter never calls us for how is mom doing, and I've tried to keep her posted by text messages mostly as phone conversation deteriorates because I don't know what to say. I always say it takes two to tango...mom is more compliant with me and I've discussed with mom part of it is my personality and I observation that mom want to be asked and not told what to do.
Is there any thought that mom can return to living alone?
Maybe mom is more compliant with meds when it's not her daughter asking her to take them?
Did the mom have a "real" diagnostic workup and not just a perfunctory "she can follow directions" at a neurologist?
Dementia is more than not being able to follow directions. It has to do with lack of reasoning skills, among other skills.
And, I would check with an expert on selling real property and the handling of assets, just in case MIL needs Medicaid down the road. Those proceeds may be tracked and I"d make sure it was done in a way to protect MIL.
But, if MIL is doing great, that's awesome. If they ask, I'd likely say that she's settled in and you are working on making sure she's comfortable. I'm not sure I'd rave about how great she is and that she doesn't seem to have the problems they claim. I'm not sure how that would help matters, but, that's just me.