I suspect that (a) she may be imagining something in the water, if there's either dementia or basic fear involved, and/or (b) there are other issues to bathing, i.e., disrobing, having someone help her, being told she has to bathe, getting cold, worrying about falling, and more.
Over the years I learned that the no rinse products are better than full immersion showers or bath. No one has to completely disrobe, get cold, worry about slipping or falling, or any of those issues.
Sometimes I even use the no rinse products for myself, especially if I'm not feeling well and don't want to worry about slipping in a tub.
If you fill the bath tub for her, and only then go to get her so that she doesn't see the water running, does she still think there's something wrong with it? I'm wondering if impairments to her vision are making her see impurities or something in the water that aren't really there. And how about adding bubbles, with a fragrance you know she likes?
How is she getting safely in and out of the tub, by the way?
Over the years I learned that the no rinse products are better than full immersion showers or bath. No one has to completely disrobe, get cold, worry about slipping or falling, or any of those issues.
Sometimes I even use the no rinse products for myself, especially if I'm not feeling well and don't want to worry about slipping in a tub.
How is she getting safely in and out of the tub, by the way?