From the time my mom wakes up she says it feels like she had to go to bathroom. She will go in morning but all day she says I have to poop every 10 minutes I had her tested and everything is normal. I eventually had to put a pee catcher in the toilet cause every time she goes to bathroom but doesn't go she would wipe.
In the meantime, eliminate all caffeine (soda, coffee and tea). No alcohol. She shouldn't eat citrus fruits, spicy foods, acid-y foods (tomatoes), black pepper, and a lot of other things. They all irritate the bladder.
Check out the IC sites online. They offer much good information about this condition and how to control flares when they happen.
In the absence of anything like this, and if this is a sort of OCD thing, sometimes a low dose anti-depressant works well for people.
I would continue to follow this up with good MD referrals.
When she says she has to go remind her that she just went and that you will take her again when it's time.
It sounds like her brain is stuck in a loop which can be normal for someone with a broken brain, so try distracting her to doing something else more fun.
It could also be an OCD behavior which is also common with folks with dementia. Thankfully there are medications for OCD behaviors, so you should talk to her doctor about that.
I wish you and your mom well.