T.A.
Hi P.,
Is it possible that you are using a different kind of margarine or butter to fix the eggs? That would be one thought. Also, it is VERY possible for someone to develop an allergy later in their life. I am 37 and have eaten eggs all my life. However, about six years ago I was tested and found that I am allergic to egg whites. I suggest that you have your daughter tested. It isn't cheap, but if you have insurance, and your doctor thinks she is old enough, test her. She could start an allergy shot regiment now and by the time she is five years old be allergy free.
I hope she gets better soon!
T. Ashe