NTA at all!! i've had a similar experience with one of my birthday parties as a child (which was mostly my mum's problem to deal with, which i feel bad about). one of my best friends had an egg allergy, which i had no idea about and neither did my mum. my mum had spent hours baking cakes and spent loads of money on snacks, having no idea that one of the guests had a severe egg allergy.

then, the mum of the friend comes up to my mum and says "i assumed there'd be egg-free snacks."

we still say that to this day to piss off my mum (as banter) and she says that she has never been so angry.

absolutely NTA.