Not "autoimmune" specifically, but perhaps someone else knows something I don't there. What
can be the case is that a new allergy and ongoing, chronic exposure
can result in fairly global "allergy" to everything. At least it can SEEM that way.
Sounds like she has at least two separate OAS things happening-- and fwiw, my DD also has had pretty severe problems with cherries, but only a few times. I don't pretend to understand that, but she eats them now without difficulty.
So. Cherries, plums, peaches, apples-- those are all birch-pollen related.
Cucumbers, melons, (and I'm thinking maybe banana??) are ragweed and generally late-summer WEED pollen related.
grass pollen offenders are less well-recognized, but I know that the list
does include peanut. And maybe hazelnuts.
Banana and avocado, though... those tend to be cross-reactives with LATEX. Just thought I'd mention that.
It is a great sign that your allergist understands the connection between pollen allergies and food allergies, btw. Many allergists do not.
What even
good allergists like that may be slow to realize, though, is that the conventional wisdom re: OAS (that it isn't dangerous, it is just annoying, etc.) is probably WRONG for anyone born after ~1995. There is no bright line between OAS and "true" food allergy-- and OAS
can become a "real" allergy to the food, sometimes without warning. Anyone that has highly atopic genetics probably needs to be aware of that, particularly if those atopic genes include anyone in the family having anaphylaxis Hx, or if the trigger is related to latex or nuts (both higher risk for anaphylactic responses).
I don't know if any of that is helpful.
Mast cell disorders
can mimic allergies, and there are some rare genetic conditions that can, as well-- but that seems unlikely in someone your DD's age.