Refuses to let go of dirty toilet paper. What is the best way to handle this?

I feel your pain. Grandma is like this. She will let go of the dirty toilet paper but only after folding it over and over again to do multiple rewipes. Which of course cakes her hands in poop. I have to regularly do a hand inspection and I have to regularly wipe down everything from the commode to the bedside handholds to the door knobs to the light switches to the chair armrests to the dining room table. You get the idea.

Riverdale, be careful with those 'flushable' wipes. We had an incredibly expensive septic repair due to tenants in our cottage using flushable wipes. And our city has posted notices in the newspaper that flushable wipes are damaging to the cities sewage treatment plant.

Some older people grew up putting used TP in a trash can, not the toilet. It may seem strange to many, but it really is not that uncommon in some communities.

I do not know the solution for Maryco, except as she suggests, pick it up, when Mum sets it down and wipe down everything Mum touches, if she has not washed her hands.

my dad always used a "hanky".(years ago, but I still remember) I don't know how my mom allowed him, as she had to wash those "things". over time I guess he stopped the hanky habit.
when he lived in AL (dementia) he would ~use~ a Kleenex and STICK IT BACK in his pocket to use again. I would catch him sometimes and try to take it. DAD, I would say, here take a clean one! but he wouldn't let me have it!
I know he was frugal, but geez dad!

Would she let you trade her the dirty TP for a clean baby wipe? Then while she is occupied with that, you could put some hand sanitizer on her hands.

There are flushable wipes out there I have gotten for my mother who has bladder issues. Hard as it may be maybe it could be explained they are supposed to be flushed. Perhaps you could suggest them as a new invention.

It don't know why but a lot of people with dementia have a "thing" about flushing their toilet paper, maybe giving her a different place to put it - a dedicated trash can or baggie - will be all that is needed. And I like the previous idea if getting it all taken care of, first the TP and then a wash cloth, while she is still seated.

Depending upon what is on the tissue, use sanitary procedures to avoid the end of the world. lol.

If bathroom time is assisted, fill the sink with water, help her wash her hands.
The tissue, if held on to, will disintegrate.

Or, try giving her a zip-lock baggie to put the tissue in by herself, avoiding a meltdown.

Or, when she is seated, bring her a hot/warm washcloth to clean her hands. Add a sanitizer to the wash cloth.

Do wash the doorknobs and your own hands.

Get her a pretty, fancy, smell good bottle of liquid soap or a pretty bar of soap, make a big deal, use persuasion, not force.

You've got this!