QFT. My own beloved Mother/Controlling Nutjob won’t change, and I know this. Which means that there are rules for interacting with Mommy Dearest:
She is never to be left unattended in my home or yard. “Attended” means that at least one person over ten must accompany her - the big kids may not be able to stop her from rearranging, adding to, or getting rid of my shit, but they can at least call me to warn me, or make note of where stuff has been stowed, etc.
If she has temporary custody of any of my offspring, the kids are strongly encouraged to telephone if Grandma starts doing things that Mommy doesn’t do, and required to telephone me immediately if there is any hint that Grandma is arranging a haircut for one of her beloved grandbabies. I swear, the woman must have been frightened by a hippie when she was younger, because she’s prone to believe that everyone looks better with hair a fraction of an inch longer than that worn by Marines at boot camp. I spent most of my childhood being mistaken for a boy, my second daughter got the little boy haircut just before kindergarten, and while I was in the hospital giving birth to that second daughter, Grandma helped by babysitting Boy 2.0 and getting rid of those pesky (beautiful auburn) curls of his!
Ma has some weird compulsion to bring crap to my house all the time. Sometimes this is a useful thing, like when she finds a sale on cereal for $.50 and stocks up. Sometimes it’s not useful, but at least a net positive - she likes to stock up her own pantry and freezer, and then realizes that two old folks are never going to eat some ungodly quantity of pork chops or Jello, so she brings outdated/freezer burned food to me. I frequently toss these items, because I don’t trust her food handling habits any more, but at least I don’t worry about her and my dad getting food poisoning because she takes that risk. And sometimes she just brings random crap, which I dispose of - donate to the charity shop, take to the recycling, whatever - but at least she’s not hoarding up her own house, so I can donate and recycle and dump a bit at the time rather than wait until I have to clean out her house one day.
I save my discussions about meddling for those times when Ma does things that can’t be fixed or have real potential to cause problems: throwing my stuff away, giving the kids medicine or supplements that I haven’t approved, sharing my business with her entire social circle, that sort of thing.