Hi Noel, that kind of sensitivity is a lot for anyone, but it seems like it would be especially hard for it to hit all of a sudden in the teen years!
I'm airborne reactive and it's very rare, so rare that many experts don't believe it exists - it's even more rare to experience a very severe airborne reaction.
I was PA all my life, but my airborne reactions didn't start until I was about 14 years old. The first reaction I had that I know was airborne was when my friend was sitting about 5-6 feet away eating a Nutty Buddy bar and my lips began to balloon up. By high school, I was so sensitive I could tell if my mom had eaten PB for lunch because my throat would itch just walking into the house after school. At first she didn't believe me, but I was right 100% of the time, so she became a believer.
For me, when I start noticing symptoms (in my case it usually starts with my face, especially eyebrows & forehead, itching), I can stop the reaction by leaving the area/getting fresh air and I always wash my hands and arms in case I've picked up residue. If I don't leave the area, my reaction will progress to throat itching, hives on exposed skin, red/swollen eyes, runny nose, wheezing, etc. I will have symptoms long before I can see or smell the peanuts, so it's important that I pay attention to the subtle early signs. I also try to avoid places where airborne peanut is likely - the school cafeteria, the grind-your-own nut butter section at some grocery stores, Asian restaurants (not that I could ever eat at one anyway), etc. For me, it's worse in enclosed areas - outside is better, but I still can't sit right by someone eating peanuts, etc.
If your DD is having anxiety, that can mimic a reaction or make a reaction seem more severe, so that would also be something to explore.