Mom won't take shower. Help!

Saw your response; sorry you and your sister have so many problems with her.  Maybe she's depressed.  Sounds like you're right that she's being selfish.  Cut the cord.  You nor your sister stay over any more.  Hire someone with her money to go clean however she can afford.  Get meals on wheels for her; get groceries, prepared dinners, whatever delivered with her money. 

If she's independent, find assisted living near you 2 sisters that she can afford, sell her house or end the lease, and get her moved.  Get papers in order so you 2 can pay her bills from her bank account and do whatever needs to be done if you haven't already.  Make sure it's a place she can transition to non independent living and will be affordable.  Check with agencies that know of affordable facilities in your area to help you. 

Good luck.

As a last resort, 'accidentally' spill milk/honey/gravy/soup on her hair and body, then get her to wash it off in the tub.

Her sense of smell could be off as happens with many elderly.  Maybe she's not able to use the shower/tub easily, or afraid of falling, or can't see good, or just tired as she said.

Make up something unless you think she can check up on it.  If Dr. will back you up to help, say Dr. told you she has to bathe face, hands, underarms, groin at least once a day to every other day or she could get a UTI or other infections which could land her in hospital.

A sliding bath chair with back that straddles tub may help if she can manage one.  Or a chair with a back that fits in her bathroom with a tub mat under it so it doesn't slide to more easily bathe off.  Type "wet bathing cloths for the elderly" in your browser, and see disposable No Rinse Cleansing & Deodorizing, and water activated ones.  Fragrance free or light fragrance likely best for less irritation in groin.  Also, soft bathing soap in a dispenser vs. bar soap may be easier for her to handle.

Dry shampoo for hair in between shampoos.  Show her how to use it, and hopefully, she will.  Someone wash her hair at least 1-2x/week; you and other family volunteers maybe.  Send her to hairdresser once a week if she can afford.  Tell her Dr. said she'd get scalp infections if she doesn't wash it more often, and then hair falls out.

Plug ins with light fragrances in hallways, bath.  Fabreze all soft fabrics and closets. 

She likely needs laundry help at her age now to keep her clothes clean.  If you can do that or get done, that would help.  May leave her with more energy to bathe!

When you visit, open the windows on any day that's nice to circulate fresh air.  Tell her you're hot, need some fresh air.

My MIL hates to shower too. So we made a schedule for 3 days a week. She puts it on her calendar so she knows the days. She has dementia and can’t remember when to wash her hair. So we have to tell her what day to wash it. Maybe u can start with one day a week and mark it on the calendar so she knows. Does she have a favorite thing to do or go someplace? Maybe u can bribe her with something. My MIL likes to go out to eat so that also works. If she showers she gets to go out.

If you've tried a lot of things already, it seems like it's going to be difficult to get her to change.

Such a yucky situation.