Most her day is spent trying. My mom is in first stages of acquired Parkinson's and complains she is constipated. She no longer can walk because of balance; therefore, I accompany her on every trip to the bathroom. She has a BM each afternoon, but still insists she needs to go at the start of each day . Sometimes, more than not, these visits last up to an hour or so by adding "just a few more minutes" each time I check on her.We have tried softeners, juices, even chair exercises. Each with positive results eventually. Like I said, she does go every afternoon. Are these physical signals she is receiving a symptom giving her a false alarm? It has almost taken over the focus for the day!
Does your Mom also have dementia? There are some on this site that have to manually disimpact their loved ones. Is it the brain that does not send the signals? Is it they are just too weak? Who knows, anybody's guess. It would be so much easier if they were able to tell us. Unfortunately with dementia it will remain guesswork.
Is she on an antidepressant? It sounds as though there is an element of anxiety/agitation here that might be addressed through meds.
Hoping someone else with some Parkinson's knowledge/experience will be along shortly with a better answer !