What Causes Missing Periods?

Me and my girlfriend are both virgins and we were fooling around the other day, and I didn't rub my penis tip against her vagina but I rubbed the dick under it you know? It didn't go in and all the while I was holding the tip of my penis, and now is her period time and it is already the 33-34 day but she moved to another country for holidays so the night and day time changed and she's under Alot of stress so is it possible she's pregnant or just late mensuration? Please we are both freaking out, reply asap.