Our long-time life companion, Cloud, passed away a while back and thought you should know.
She had had a stroke at some point and would fall down each step but then somehow kind of healed herself from that and lived a year or so longer. She never adjusted to having the two newer cats in the house and seemed unhappy since they arrived. We didn't know the optimal way to introduce them, not that in Cloud's case it would have improved their reception.
I think her being the Queen of the house--and then suddenly not--
rubbed her the wrong way and I'm truly sorry about that.