It is a tough process but MIL is exactly where she needs to be at the moment.
No-one knew MIL was deteriorating until FIL passed from cancer and then, because she was always a difficult person, it took a really long time for the grieving family to realize she wasn't being difficult, she was incapable of self care. Over 2 years, first there was outdoor lawn/snow workers, then there were inside cleaners, then a meal service, eventually a private cook who became a caregiver, then another caregiver, then cameras she would turn around, then another caregiver but the caregivers were taking advantage of her, one moved her husband into FIL's old room and SIL discovered this because a strange mans stuff was in her dads room. Whole situation was tough because MIL was a nurse and aware of a lot of things she should do or say on a good day to get her way so she seemed coherent enough to complain to the Dr's about all sorts of things but was making things up (this was sadly her normal personality) but she was also utterly incapable of self preservation of any kind. She was like a smart toddler who sounded capable but wasn't so it was very tricky to get the Dr onboard.
MIL has been in care for maybe 4 years and 3 memory care places so far. The thing is these places have staff turnover and policy changes like any other business so someone needs to watch for changes. The first place was picked mostly because they had a free spot and getting her in was so necessary, it was lovely for a long time but then MIL wasn't being bathed and they left her uncared for a few times too many so off to the second one. The second spot was great for about a year until a bunch of staff just quit unexpectedly, or was fired, whatever happened was super disruptive and MIL fell (but told me she didn't fall - that was sketchy) so they pulled her out of there and moved to the third spot. Now in the third spot she seems well cared for and is clean and eating regularly.
I suppose my biggest takeaway is to NEVER conceal someone's deterioration from other family members because if something happens and everyone is left playing catchup the consequences can be awful. It was hard to watch all this play out & it would have been much easier if FIL had been honest and told someone, anyone, even MIL's Dr what was going on so the Dr could advocate for MIL but since FIL didn't reveal anything to a soul it was uphill all the way as it is very difficult for adult children to intervene with an uncooperative adult parent. Second take away is if a loved one is in a facility someone needs to pay close attention to what is going on with staff and standards of care because things can change rapidly and no-one is going to tell you as things slide downhill, you need to see it for yourself. One random hour a week can tell you everything, smell the room, show up at meals, look at all the other people and the facility and listen to how workers are talking to other patients.