Grandma is washing her hands and goes back into her room to poop. Why, grandma? Why?

I take it that she has been diagnosed with cognitive decline or dementia? That kind of behavior isn't unusual for someone with that condition. They may do all kinds of things that we don't understand. It's just that they are not able to think clearly or process information. That's why they do unusual things. Toileting seems to be a very common theme for odd behavior though. She may be at stage where she needs constant supervision with her toileting.

Have you read the book entitled The 36 Hour Day? It's a guide to caring for someone who has dementia. It offers insight and practical advice.