Self-evacuation...

I care for my 72 Yr old MIL with Moderate dementia. She is obsessed with pooping. She says she feels the need to go frequently, but I suspect it's just gas pressure. She can not tell the difference. However this obsession with trying to poop 15 times a day had her Self-Evacuating her bowels. She is not constipated. She actually has soft stools, but tries to force herself to have a bowel movement so frequently that a proper stool never forms.

I try to go to the bathroom with her, so I can supervise and stop the hands from going back there, but she is so obsessed she is at it every 15 minutes. It's almost like she waits until I am busy... I have thought to lock the bathroom, but that seems wrong. What would you do? We have children in the home and she doesn't wash unless I am supervising.

She would be miserable in a home, but this behavior is very unsanitary. Please advise.