I discussed this with her doctor and he agreed that rearranging things in our home can confuse someone in an advanced stage of Alzheimer's Disease (plus she also has Vascular Dementia). What happened is my sister quietly took the decorations and tree down before any of us were awake, and rearranged the furniture back to the way it was. When my mom woke up, she knew something was missing, but couldn't pinpoint what was wrong. She began accusing my sister of stealing, being passive-aggressive, being aggressive, being violent, etc.
My mom didn't know what was "stolen" but came up with a different item all the time, whether it was her pajamas, suit, kimono, and even scissors. She had no clue what was missing, but assumed it was something of hers and that the only person she could think of that would steal from her is my sister, because she was the one moving stuff around.
My mom has nothing to steal. She has nothing to even borrow. My mom is 5 feet nothing, probably 90lbs soaking wet, and in Alzheimer's has poor hygiene and very poor taste in "fashion." None of us are that little, that desperate, or in whatever era of fashion my mom is in. How can one steal when you live in the same house? All of us work and buy our own stuff. We buy my mom stuff, and in more recent times, much of my mom's stuff is gifted to her through Amazon by my amazing friends. My mom does not own a suit, kimono, pajama set, or scissors. She was very adamant all those things were stolen from her, constantly changing the items that were "stolen."
That said, NO Christmas tree this year, not even with a barrier to keep the cat away. I did find some cute ideas on Pinterest (actual link to my pinterest board) such as hanging garland over the doorway, and maybe some bulbs hanging from the window sill. Things that are higher up from the floor and away from the cat. We shall see!