need advice on keeping colostomy on alzheimer's patient

patient is a pleasant lady who has diagnosis of alzheimer's. has had a major decline past few weeks. up until 6 a few weeks ago, was maintaining colostomy (old one) with nursing oversight/minimal assist. suddenly, she has begun removing colostomy bag and placing it in her pocket, or wherever. she refuses to wear disposable briefs at this time (removes them). the colostomy she currently uses is the type with the foundation wafer and "tupperwear bag" that snaps on. her skin is too fragile for the one peice adhesive bags. anyone had this problem? any suggestions? she is ambulatory and still is continent of urine most of time. thanks in advance for any ideas.