My heart goes out to you. I worked with a lady whose son had severe peanut allergies. The child had epipens and benedryl either on his person or in the possession of his teachers/caretakers at all times. The thing is, don't ever hesitate to give the shot -- the few seconds you buy to get Shelby to the vet can save her life.
The mother was given "lessons" on how to use the epipen and even practiced on an orange -- she did in fact have to use one, and she was greatful for having had some practice.
I wonder if there is such a thing as an epipen for small dogs -- seems like there would be