It's difficult situation, use a trick to save your mom, from a difficult situation.
Replace your mom with exercise ( well, as you mentioned her nature she must disagree so I again have intelligence to tell them to do exercise for urinary bladder for frequent urination , she can't deny , and she can practice it during go to toilet and come because as i understand her time duration in toilet )
Now exercise must be most selective and should be one or two in numbers.
I'm sure this exercise trick along with other medicine is useful.
Exercise is simple , told her to squeeze her inguinal area .
Progression - 5 sec hold * 10 times ( 2 week)
10*10 .
Next Steps
try to create a atmosphere of exercise by posting banner on toilet .
Health Tips
don't try to personally involve with her , you play a game for her brain to become curious about exercise .