Tatt. just seen this. The only thing I can say is... that you know more about Epipens than I do (actually, most that I know I learned it from you).
My only advise for a long haul flight would be to take all the paraphernalia with you. I don't remember if your girl reacts by skin contact too, and if so, I would take the following with me:
-Desinfectant towellets to wipe surfaces around you, a small blanket to cover the seat, I carry both medical kits with me on my hand luggage now (4 epipens, 2 bottles of piriton, etc (remember to bring it in bottles of less than 100ml all in transparent small ziplock bags), Some snacks in case the food is not what you ordered (it did happen to us on that flight too). It helps to get the medical notes too, in someway it gives you credibility in the security checks and allows you to bring the epipens in, and in our case, those notes helped the doctor who happened to be onboard to know what to expect.
The stewardesses were fantastic, so where the doctors on board and other epipen users who poured in to give advice.
Please don't forget to ring the airline to tell them about the allergy, write down when and who did you speak to, remind them at the check in, remind them at the gate, ask to talk to the senior stewardess as soon as you board the plane. The sooner the message is given asking people not to consume their own nut products onboard, the safer the environment will be, but keep an eye on things, peanut crumbs can be laying here and there (Not trying to scare you up but... it was crumbs on the floor that caused DS' reaction)
Hope that has helped (I know that it may not make it easier but some precautions pay by, we have taken DS on trips abroad in many other ocassions since that trip and things are becoming much easier.
Good luck,
Chandra