My mother forgets to turn off the faucet after she uses it, what should I do?

My mother is getting to the more forgetful stage of Lewy Body Dementia and has now started to repeatedly forget to turn off her bathroom sink faucet after she's used it. Which sometimes can leave it on for hours at a time before I hear it. Thank goodness we're on well water so we don't have to pay by the gallon. Turning the water off entirely under the sink isn't an option because her dementia is such that she can figure out how to turn that back on while still forgetting to turn the faucet off at the sink. I've looked at touchless faucets but they generally don't offer temp adjustments. She still likes to take spit baths so if I set it for cold only, that's not going to make her happy. If I set it for warm, she's not going to enjoy it for drinking. At this stage I feel like a hamster in a wheel trying to figure out a viable solution. Any suggestions?? Help!!