I don't know your story, so I could not know what's going on. Ask a doctor about it.
It could be PTSD, if you've had much trauma; it can sneak up; however, it could just be a food allergy or some other kind of anxiety-related issue . . . first date . . . too embarassed to call the girl back?
There's nothing really to be embarassed about, regardless of the cause of illness. Illness (physical or mental) is a human thing and the girl wouldn't be much of a human if she had not called you back.
I hope you call her back and don't make a big deal of that incident . . . maybe go see a movie that's non-violent next time, if you suspect PTSD.
Talk to a doctor, though! Please. It could be any number of things, hun.