My mom will hide dirty underwear I think she is embarrassed and not sure what tO do

Could you give her a covered bucket to keep it in rather than hiding it in her room? Then you can just dump the bucket into the toilet. Probably no use arguing or reasoning with her. Hopefully this is a stage and won't go on too long.

my mom does this (as well as the hiding food that was mentioned above) -- she also flushes non-flushables in the toilet. We have not found a solution. my mom just looks at me or my brother and responds with, 'well, that is how i do it.' she doesn't see anything wrong with her behavior and she used to be such a clean and germ conscience person. we are getting to just monitoring her bathroom time.

Haven't found a solution but my dad wraps poop in toilet paper and puts in garbage can in his room. I get extremely frustrated with this one too! He has no explanation when I try and ask..just a "that's what I do with it".

I had a patient that went into the kitchen at night and brought back food into her room and hid it but not bm. Hopefully she will forget that behavior soon. I have no suggestions for you other than supervise her bathroom trips.