I doubt she was experiencing a true allergic reaction. Although it IS possible to be allergic to semen, the symptoms are usually localized (pain, burning, swelling in the vaginal area, for example), and occassionally, anaphylactic-type reactions could occur (difficulty breathing, hives). Either type of reaction is extremely rare. I bet she had some sort of psychological issue.
A new boyfriend/girlfriend is ALWAYS associated with more pleasant feelings, my friend. That's because they are new.
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?