How do I address the issue that my mom continues to wipe herself when using the restroom and she does not do anything?

I went through this with my DH aunt. It was a phase of her dementia. I reduced the amount of TP in her reach. she would go into another bathroom and take the TP. She would use paper towels. We had to keep the paper towels out of sight. I tried using thinner TP hoping it would flush easier. Nothing worked and she kept clogging the toilet and yes there were big plumbing bills. I didn’t think of a bedside commode so I didn’t have that experience.
She was still able to go to her bathroom on her own and didn’t have 24/7 care when this started. Finally I bought a commode that advertised that it could flush a bucket of golf balls. (American Standard brand). This solved the problem of the clogged commode if not the waste of paper. Even with that commode, we had to use the plunger from time to time. But I never had to call a plumber for that problem again.
She is now totally incontinent and bed bound and in a nursing home. This past week she told me a story about needing to go to the bathroom that morning and when she tried to go to the toilet, someone else was in the bathroom. Of course this didn’t happen.
She hasn’t gone to the bathroom on her own in at least a couple of years, maybe longer.
She told my husband once that in the NH when she pressed the call button, they didn’t come, but “it” did.
I doubt she has ever pressed the call button but if she had that would have been the result. A CNA nor a Nurse is going to rush to her room when the call button is pressed.
The truth is what stopped her from clogging the commode was her inability to walk.

If you want to keep mom living at home at 100 years old, then she needs help in the bathroom each and every time she goes. That's not negotiable. You will govern how much toilet paper she uses and how long she sits on the pot wiping herself, thereby avoiding clogging issues and plumbing fees entirely.

Best of luck to you.

You’re not going to get through to her because she has lost the capacity to understand what you’re telling her. You might as well save your breath.

When this sort of thing happens, it’s time for 24/7 care by professionals, hopefully not in your home.

Others will suggest that she be tested for a UTI, which is a good idea. But even if that is treated and goes away, she’s still going to have the cognitive decline that keeps her from functioning as a normal person. I’m sure that you’ve noticed other evidence that she’s not thinking clearly or doing things in a reasonable way.

How many plumbing clogs are you willing to endure before you find appropriate care for her? It’s time now to start looking.