Yep about a week before Xmas I developed a sudden allergy to 'something', just couldn't narrow down what it was (mainly cos I hadn't eaten anything new).
Took me a few days, and quite a few episodes of swollen eyes, lips and fortunately only a scratchy rather than swollen throat, to narrow it down to....tomatoes!
I can live without the tomatoes in summer salads and on sandwiches, which is where we're at at the moment, but i'm not going to be a happy vegemite come winter and i'm struggling with lasagna.
Hope your gf figures it all out YourYumminess...tis the not knowing which is the worst. And a word of caution, some reactions to allergens get worse with repeated exposure, so her next reaction could potentially be worse than the last one.