Because nut allergies are more likely to cause almost instantaneous death from anaphylactic shock.

I'm not intending to be argumentative nor belittle the suffering of people who are allergic to animals but forced to sit next to them. You should not have to put up with it. But the fact is that most (not all) pet allergies are not life-threatening. Most (not all) nut allergies are.

My husband carries an autoinjector of epinephrine and adrenaline to keep his heart beating and airway open in case he accidentally ingests tree nuts. His doctor predicts that, even on the ground, there's no way an ambulance could get him to a hospital alive if he doesn't use that injector before he passes out.

And while I know some people can suffer dangerous asthma attacks and anaphylaxis from their pet allergies, fast-killing food allergies are much more common than fast-killing dander allergies. I think that's why airlines are more sensitive.

I'm sorry for your daughter's discomfort, however.