Hi, at the age of 15, while at Red Lobster, I discovered that I am allergic to shrimp, crab and lobster!!! And, like your daughter I have asthma. I must have developed this allergy because I used to eat crab every summer. My brother has the exact same problem.
I can eat and love other fish; I can even eat clams and mussels. I've never gotten tested for exact allergens, I simply avoid crab, shrimp and lobster and have had no problems. I get the same effects as your daughter if I do eat them---swollen eyes and throat...I ate lobster once (I knew I should not have) and my throat started to hurt. Turns out my throat was swelling to the point of covering my windpipe. The dr. gave me a shot of Benedryl and told me not to eat it again (He hasn't had any trouble out of me since!).
Cathy