12 years on, does she still have reactions if she eats beef? Does she (or maybe did she) have any reactions to other mammal proteins (milk, pork, etc)?
This was also driven by some long term low to very low iron levels, and supplements weren't doing the job. She had to get some iron infusions, which isn't a pleasant procedure.
Once she started eating beef again, her iron levels came right up.
In fact we just got back from Safeway with several pounds of medium lean ground beef for dinner tonight and tomorrow.
It took us both years before we even considered testing her reaction again because of how bad it was before.