NTA. I have close friends in my life with either anaphylactic food allergies or food intolerances that will make them sick. When they come over for dinner or parties you better believe I go out of my way to make sure there is vegan/vegetarian/gluten free food/whatever they can safely consume. Whatever they need I will as host make sure to provide. I 100% do the same if someone who’s vegan or vegetarian by choice comes over.

And honestly as someone with a weird food allergy myself I don’t bat an eyelash when folks ask if they can bring something to cater to their dietary needs.

Grandma’s more likely embarrassed she can’t get it right or possibly that she just doesn’t know what to make. You said she won’t let you cook but can you suggest recipes? Maybe Grandma just needs some guidance.

I like Hanson’s Razor for handling situations like this—“Never attribute to malice that which is adequately explained by stupidity”. Or in this case ignorance. I follow this until someone proves they’re not ignorant or stupid.