Congrats on the way you handled this situation. I thought about her all evening!!
One of my children's best friends has a nut allergy among many other allergies. IT IS A REALLY BIG DEAL! He is a teen and only allowed to go to friends houses who have training with the epi pen. I keep an emergency contact list for him on my fridge. He only eats food provided by his parents.
My husband's colleague died after eating a candy bar with a new "nutty" recipe.
Good luck.
Maybe have parents provide food from here on out?