I would continue to check on her until you go to bed. If there are just hives, and no breathing problems, she is probably going to be fine. Can you contact the pediatrician or nurse after hours line to feel better? Oh wait - you did. I have to say I agree with them. Be careful with NO further exposure, and allergy testing as soon as your doc will allow.
Has she gotten anything else today that is strange.
And unrelated, when was her first birthday, and has she had the MMR shot or chickenpox shot recently?