Why did not you use condom for precautions? If she was quite wet then she could get pregnant even if you did not ejaculate inside her vagina but at the entrance of her vagina because sperms are good swimmer. Tension could also make periods delay so ask her to be tension free.
However, it would be better if she gets herself checked up with urine pregnancy test kit and confirm whether she is pregnant or not. If the result is positive then without making any stupid mistake see the gynecologist and ask her to help you people.