No, she didn't have a heart attack, heart attacks do not cause convulsions, she had a seizure most likely. As the others have said, a lot of things can cause chest pain. Yes an underlying heart problem could cause chest pain, but just because she experienced chest pain doesnt mean she has a heart problem. Many things can cause chest pain such as indigestion, anxiety and asthma.
This is not good, and the fact that its happened before suggests that there is something very wrong. Tell her to go and see a doctor and soon, if she hasnt already, even if that means telling her parents, this is not right!