Making accommodations that become ridiculously onerous--and still don't guarantee safety--is the kind of thing that looks good on paper but, in the long run, causes more harm than good.
One option is to keep the child home and use a speaker to connect her to the classroom. I know of situations where this set-up has been used for kids who were in body casts or had other conditions that made it unsafe/unwise for them to attend in person. In many cases, this option has worked out well. If her allergy is life threatening, this might be the safest choice--not because anyone wants to exclude her, but because it's just too dangerous to do otherwise.
I understand that the goal here is to keep schools
from getting rid of kids who pose challenges. But surely there has to be some sense of balance, both for the sake of the kids in question and for everyone else involved.
If a child had SCID (aka bubble boy disease), would the entire school--including the people--have to be encased in plastic? Or should there be some recognition that this is neither practical nor reasonably attainable nor even safe for the child even if it could be done?
The laws governing school access should require reasonable
accommodation, not turning the place upside down for the sake of a single child. And education should be guaranteed, even if it has to be provided in creative and unusual ways.