Goodness, that's awful! If she also has a urinary tract infection, that can be quite uncomfortable and it 's beyond bizarre for any doctor to refuse to treat it.
Should she perhaps be seeing her primary care physician instead of her gastroenterologist for the problem? Going to an urgent care center for a UTI is another option.
As far as chronic diarrhea goes, I hope your aunt has thoroughly discussed possible causes with her doctor.
The anti-diarrheal over-the-counter medication
loperamide (generic name) can help control it. There are also prescription medications for severe diarrhea.
I wish your aunt the best.