[mslif]

A girl is most prone to getting pregnant 14 days after the first day of her last period. (Just an FYI)

Thw symptoms you describe do not seem like pregnancy symptoms to me but all women are different. If she is taking birth control pills, she might have developped complications from it or could just be getting the flu.
Go get a pregancy test, they are very accurate nowadays. If the symptoms persist, take her to the doctor. I understand that she has a social disorder but her health is more important.