It sounds like your girl had a pretty severe and potentially anaphylactic reaction. Anaphylactic reactions do have a high percentage of being fatal. Your fast action was good. She may need to stay at the hospital for a few days if they don't get an immediate response with steroids and antihistamines. Since reactions can continue for several hours after the initial incident it would be ideal to have her stay at the hospital. I would be sure to ask your vet for emergency drugs to keep on hand in the future should this happen again.