So I recently stopped locking my room's door at night because there's a network cable that needs to go outside into the living room and there's no reason to remove and re-attach it every day. Anyway, this has triggered my grandmother's terror of people coming into my room to take my keys and subsequently using them to unlock doors in the rest of the house. She insists they'll 'dirty her makeup' and 'poison the food'. We've had no history of break-ins, the main door is locked, and I just want to leave my room door unlocked like any ordinary person does with their house.

Anyway this morning my grandmother came into my room, took my keys and hid them away in a locked room because she was afraid someone would take them and use them for dubious purposes otherwise.

Now she is going on about 'I wanted to return the keys to you! But I couldn't, because it was very dangerous! They might put things in your mother's makeup and make her look like a monster if she puts it on!'

I think she is also trying to humiliate me into giving in to her demands, because she's demanded that my access keys to the fridge (it's in a locked room) and toilet be taken away, and is talking about buying a pot because she clearly can't let me have access to the bathroom since my keys are so easily compromised now with an unlocked door.

She's been like this since I was a kid and she is otherwise in total control of her mental faculties (she doesn't have dementia, can remember things very well, can make decisions, and is always looking out for herself). Does anyone have any pointers on how to deal with this kind of thing?