LOL too familiar. Dad has Lewy Body. Same thing. Since he's moved to AL, it's a bit easier because their shower facilities are set up better than at his house. But it still becomes a battle and they can't force him. I think for my dad, it is totally about control. It's one of the few things he still has control of. But after a few weeks, the AL really starts to push. It's a continual battle for everyone involved.
Check out this post: https://www.agingcare.com/questions/how-do-i-convince-mil-that-she-needs-a-shower-453418.htm
I'm sure there are others, but that's the most recent I can think of.