If you feel that the reason your mom isn't bathing is that she thinks she has already taken a bath, or that she just doesn't see the point, try tying her bath to something fun. Say something like, "Let's both get cleaned up and pretty and we'll go for lunch." This could nudge her into thinking it's worth her while, and even fun, to spruce up.
Make sure the shower and/or bath are safe and comfortable. If the bathroom tends to be cool, see if there is a way it can be warmed up before a bath. If a shower is the best route to go for the person, install a grab bar to for stability while getting in, a comfortable stool to sit on and a hand-held shower head. This type of shower head keeps the water from continually coming down on the person's head, so the elder is forewarned when it's hair washing time.
If dementia, such as Alzheimer's, is so advanced that the elder is frightened of water, or scared of the tub or shower, you may want to try a different tactic. A person can get clean with sponge baths.
Whether you are using a sponge bath method or helping the person with a shower, talk about what you will do next, taking into consideration the person's dementia and where they are mentally. Don't surprise them. Describe your every move in a low, soothing voice. Say, "I'm going to wipe your face with this nice warm cloth, okay?" "I'm going to lift your arm and wash, but I'm keeping you warm and comfortable under this blanket."
Find products like dry shampoos so you don't have to wash hair as often.
Take privacy and modesty into consideration. Some people, don't want family or others close to them to bathe them. A Senior Care service may be able to cope much better than family members.
Remember that a daily bath isn't necessary. Also, please ask yourself if all the fuss is because of your own standards and what people will think of you if your mom isn't pristine all the time, or if it's really about her health and comfort. Try to compromise. Yes, cleanliness is important for good health. But a complete bath or shower daily is not next to Godliness. It could be closer to torture for your loved one. Try to find alternatives and a middle ground so that some sort of hygiene is maintained with a minimum of unpleasantness.