My grandmother is incredibly stubborn and think she is fully independent. When her mind tells her she has done something there's nothing to change that fact no matter what I say.
When trying to make her take a bath her daughter first started approaching just by saying its time for the bath like always she used to bathe in the afternoon. Failure after failure when we came visit grandmother smelled horribly and her daughter says she hasn't bathed in weeks. She then turned to saying to her that she stinks, that's when we got a lenghty phone call from our grandmother telling us her daughter said she stinks, but she DOES we just never tell her that.
Now her daughter moved away she couldn't take anymore and grandmother is left to us. We tell her to take a bath and she always replies she already has. We started with telling her bath is ready, made sure everything was great, we have great facilities for her to take a good comfortable shower.
If we go all out and debate her she hasn't taken the bath she will just want to leave the house and go to her old home, as if she could. Adding new things to the bathroom like most advice on the internet is a complete waste of money we now think all them are just to sell us things we don't need because what good would getting "X" thing for her shower would do if she won't even get off the sofa to go and see it. We could get all the things in the market and the problem doesn't rest there it's getting her to the bathroom to take the bath. After daily attempts we keep trying as she starts to smell worse and worse our only successful plan was to put a really sticky and grossly bothersome shampoo on her head wherever she is currently sitting and after it starts to slide across her head it would start bothering her and she then goes for the shower. Problem now is that's the only way. Recently this "already have done" thought in her head has spread to food now, so she is starting to starve herself. Luckily we've gotten her OTC meds to make her hungry and have a stock of her favorite food she never says no to. We've gotten no useful advice from multiple "doctors", from her concierge to neurologist and all they seem efficient at is charging the medical plan a hefty lump sum. So family won't do it, doctors won't do it, I look now for advice over the internet to see if somebody would give us the answer to all riddles without seeking a million dollars.
I finally told her that if she refused to bathe and wash her hair of her own free will then I would hire a nurse to come in and bathe her. After she screamed and yelled at me and called me every name in the book and told me I was going to find myself sitting in the street looking for a new place to live, she went into the kitchen and washed her hair and then took a bath. She took a bath every single day for about 4 days and then she began slipping but it hasn't gotten back to the two week intervals.
It think this is all trial and error in figuring out what to do. I can tell you that water that seems warm to us, for some reason is hot to them, so let them adjust it to their preference.
God Bless Us All!
All that set up, now you have to be creative. The sticky hair thing you're doing is workable. stealing something stinky on her blouse maybe. My moms toilet was right next to her shower. Once she was sitting down, should have to have her trousers off to change her pull up undies (depends diaper pull-ups), so we were halfway there. All I had to do was show her that her blouse was dirty from food or whatever and get her to remove it so we could change it. Once I had all of her clothes off, I just said okay time to step into the shower. She complied almost every time and the time she didn't want to we just wait a little while until she was willing, which she eventually was because she was sitting there with no clothes on. I found that the trick was never to tell her in advance that it was shower day. I would just wait until she went into the bathroom, give her a few minutes of privacy, then go in to "help" and do the rest as already stated. Let us know how you eventually work it out with your grandmother.