Okay. So what do you do about it?
This is a case where compromise is essential. Third parties can also help. While my mother-in-law was still in her apartment, she didn't remember to bathe and didn't change her clothes, though she'd look me in the eye and say she had. And she believed she had.
Some of this was memory. She thought she must have taken a bath somewhere along the line, so she said she did. However, I feel much of it was fear. She was afraid of the shower. She was afraid of getting in the tub. She was confused by it all. Denial was easier.
Also, she was an exceptionally modest woman, even for her generation. I knew that she didn't want a family member helping her take a bath. Far too intimate. Our "solution" was to get an in-home care agency to come in for the sole purpose of a bath. That effort was better than nothing, but only moderately successful. She grudgingly let "the girl" give her a shower the first time. I stayed in the apartment, but in the other room. Then, a different woman showed up the second time. My mother-in-law refused to let the home health worker in the house. She slammed the door and that was that. No luck. We tried again. She gave in that time, but it was touch and go. So it went.
This behavior came from a woman who was typically very mild-mannered. She was sweet and gentle and not one to "act out," as they say. The fourth time the agency sent someone, a woman of another race came to the door and my mother-in-law, who had never shown anything but love for others, suddenly became a bigot. She grew up in an area where everyone was rather generic in looks. I think her mind was back there, and she didn't understand a woman from another country coming to her door and wanting to give her a bath.
Actually, it's all understandable. I wouldn't want a stranger coming to the door and telling me he or she is going to give me a bath. But caregivers need to do something, and often an in-home agency can be a good choice. Some agencies are more careful than others about the consistency of caregivers. That helps immensely, as then that person arriving means "bath time," and if the person's memory isn't too bad, they may even remember the caregiver who arrives. But we weren't so fortunate.
Thankfully, a room at the nursing home we were waiting for opened up, and when my mother-in-law settled in there, she grew more comfortable, and baths were no longer a problem. It was part of the routine.