She had rectal prolapse and was going to the bathroom a lot and was using 2 rolls a day. After the situation was corrected she is using one roll a day. It’s either going to cost plumbing problems or break her. Is there anything I can do? She does have dementia.
If she has her own bathroom, shut the water off on that toilet so she cannot flush (if there is a way to prevent usage altogether, by all means do that! If not, you'll just have to scoop out the paper yourself? EEEEuwww - not pleasant, but neither is a recurring plumbing bill!)
If there are only shared baths, perhaps replace the door handle with one that uses a key to lock it and encourage her to use the portable?
The key can be hung by the door, but up higher where she cannot reach it. If you have young children, they will have to be trained to get one of the adults to help, but it is easier to train kids than someone with dementia.