I agree-- never that great an idea to force a child-- must less trick one-- into a food challenge against their will.
What I wonder is if you've approached the conversation as one of being lower-impact
on those around her. This
is something that factors heavily into my DD16's approach to life with food allergies. For example, she would probably never have done an open egg challenge without that facet of things. It was a matter of being old enough to want to give dating partners more freedom in their own diets, to give friends/family more freedom in their own kitchens, etc.
She could care less about eating eggs-- EVER. But her poor fellow college students certainly do care, and it makes life far easier in other ways if she knows that she simply doesn't need to worry about X at all, ever.
Does that make sense? Because at it's root, the reluctance to evaluate the severity of the allergy is a food
preference (albeit a serious one, which I understand is NOT the same thing as "I'm picky/I don't like that") and not a matter of safety.
For my own family (and I am not for one instant judging what others do or do not here) we evaluate our "footprint" with others and our justifications for making such requests of them on the basis of what is NECESSARY, not what is convenient, philosophically consistent, etc. for ourselves. If I have to ask for no shellfish at the local potluck in order to be able to eat anything (or just to attend) then I'm only going to be comfortable doing that if I
know that my safety is on the line.
I'm not sure if this makes complete sense or not. I just don't ask OTHERS for accommodations that I don't
know that I need. That is, I do every thing in my own power first, and only then ask others. It's a philosophical position on allergy management, I suppose. Which is why I-- truly-- don't judge others for doing things differently-- I just offer that as another facet to the multiple things under consideration.
Not all 12yo may be ready to see things through that lens, either. Mine was, and Mac's DS as well, but neither of them are typical teens, nor were they typical as tweens.
Good luck, and I'm

that you won't ever have to deal with it as an allergen, either way.
Tissue culture derived vaccinations and drugs
might be a concern to someone with a chicken allergy, by the way. Not a big one, and probably most people wouldn't need to worry about the ultra-trace amounts in question even with an allergy in play-- but it's worth investigating if you happen to be someone highly sensitive to an avian allergen.