YANBU!!! It's irritating and it's thoughtless! I run a totally GF house at home, so I just never have to worry about it. I can't imagine what it would be like if I still lived at home, or in a house share.
At my parents house I cover the grill with tin foil before I use it - I know it's always clean then, and have a "side" of the kitchen. But mistakes are still made. They're very good at cooking GF, but not so much with cross contamination. Like, I have my own butter there - great - but they will then offer me cheese with crumbs on it... so they sort of understand, but not entirely.
And I can still remember taking a swig of my glass of squash at my in-laws, and realising it was barley squash 🤦🏼♀️ my MIL was mortified!
My mum is generally a wonderful woman, but definitely in the "I don't believe in allergies" camp - even though she watched me get sicker and sicker for several years before all my tests. Her response to me and my sister having allergies, eczema, asthma etc. is "well, I never wrapped you in cotton wool. You were fed everything. I don't know why this happened."
I also have oral allergy syndrome, so in the UK I'm allergic to loads of raw fruit and veg and some nuts. My mum never believed me as a child when I told her my mouth was getting itchy, until the allergy got worse, and my lips started to swell too - which she could obviously see. But even now she's skeptical!
Read any thread on allergies, and you'll find the "I don't believe it / it never used to happen in my day" brigade. Doesn't matter what info you provide, or how many people die and make the news, they still don't believe it. Autoimmune diseases I should imagine are just as tricky for them to get their heads around.
Keep your food in boxes in the cupboards and fridge - padlocked if you need to! and no I'm not joking. And move out as soon as you are able to. You can't trust your mum with your health, so you need to be 100% responsible for it.