Did she play a brass instrument by chance? Some mouthpieces are leaded brass. Also some players also have reaction to brass.
Every time I mention this people kind of look at me funny when I offer my co-trigger explanation as "some kind of bug", but I was reading Dawkins at the time and had come to stop thinking about unitary causes for phenotypic expressions.
Of course, that's not the easiest course of conversation to travel down with most people, so I just sort of accept the silence that follows. It does give me the fun little anecdote of how my daughter was deathly allergic to peanuts for a year, but then she got better.
The classic example is H. Pylori in stomach problems. I doubt that it's a lone outlier.