My mom with dementia is obsessive over her bowel movements. Any advice?

In your profile you say that you leave your mom by herself in the bathroom and she rings a bell when she's done, but she by then has often wiped herself from front to back.
So honestly the best solution is for you to stay within sight so she can't wipe herself as getting a UTI can and will in most cases make her dementia worse, and if not treated properly can lead to more serious issues including death.
Your mom is like many older folks who become obsessed about their bowel movements, and a lot of those folks don't have dementia either.
Please don't let her wipe herself anymore, as you're asking for trouble if you do.

Oh gosh, it definitely is an obsession with the elderly! Just ignore it. I honestly don’t know what I would say if asked this question 😝.

I had a biology teacher in school who went on and on about poop! LOL She was batsh*t crazy! One time she asked our class how closely we examined our poop!

Needless to say, our entire classroom went into hysterics laughing 😆. Then, we got into trouble for laughing at her!

Wiping from the front can cause UTIs if not done right. Toileting was not my favorite thing. I prayed Mom wouldn't have one everyday. You may have to keep doing it yourself. Her talking about it I think stems from potty training.😁 If it was me I would have told Mom that was gross and I was not talking about it.

I don't know why so many elderly people have an obsession with poop. I guess you really can't stop her from thinking and asking so just be ready with some vague or even silly answer. Your answer doesn't really matter so you can have a little fun with it. I would stop stressing about her wiping the wrong way. It may happen. Maybe you can use a wipe on her afterwards in case she did it wrong before you got there. If she ends up with an infection, you will have it treated and she should be fine. There are so many things to keep an eye on!