My 90 year old Mom in assisted living refuses to shower. Any suggestions?

When my mother entered assisted living she too started refusing showers. Her caregiver was concerned with moms steadfast refusal. At about 6 weeks in I stepped in and tried reasoning with mom about bathing. She insisted when she was ready to bathe she would. We told her we would restrict family outings if she she refused to bathe, we were told by her if we had to put conditions on being around her stay away.
The next try was to restrict her from outings she liked like taking walks, or trips to primary doctor who she adores. She was told couldn’t do these things unless she bathed.
Things still not great on bathing front but, not being so demanding about it we are at a shower about twice a month, and hair washing monthly. We try sponge baths in between. The shower situation is truly a balance of choosing your battles.

Is she okay other than not showering? Does she she have any negative health issues due to it, like UTI? I'd discuss it with her doctor and see if there is any reason to insist on the shower or if the sink bathing is okay. If things are fine otherwise, I'd address the smell. Does she smell due to some infection? I'd think the sink bathing was good enough to keep body odor down.

Another option is to use this time to get recommendation for a higher level of care, like Memory Care. Their staff is trained and they seem to know how to manage resistance. When in regular AL, my LO refused any kind of bath, but, once in MC, she never gave them a problem. They worked with her and soon it was not an issue.

What about a sponge bath

For my mom it's a privacy matter, so the care giver makes sure my mom isn't seen naked by anyone while showering. I'm not sure how this happens. I guess she lets my mom undress in the shower with the curtain closed while sitting in the chair. My mom hands her clothes out and the care giver turns on the shower and my mom washes herself. Then a towel is handed in and then clean clothes. It must take forever to accomplish. I don't know where this modesty came from because she was never like this before. We girls, my mom, sister, and I, always tried on clothes together in the same dressing room at stores and at home. It would be good if you could just figure out exactly what your mom's issue is with bathing and try to provide whatever she needs to accomplish a shower at least once a week.