Why is my mom washing her clothes in the tub instead of letting me wash them in the washing machine?

My mom is not putting her clothes in the hamper for me to launder anymore. She has been washing them out I guess in her tub by hand. Anyone have any idea why someone with middle stages of dementia would start doing this for no reason. I told her that the dish detergent or shampoo she was using would give her an infection but she still does not listen and is still washing by hand. I bought her some cold water detergent like woolite yesterday since I can't get her to let me do the laundry. She lives with me and I keep going upstairs to get her laundry and there is none. Is it ok to just let her wash them by hand or should I do something?. She can no longer remember how to use the washing machine and I think that is part of the problem and she does not want to add more to my plate...