Take a drug call "Plan B"
go search for it and read about it
Their is a possibility, just watch for signs and next time be more careful.
There is always a possibility that she can be pregnant. How ever it is almost impossible for her to be, because ovulation takes place 14days after a period ends.
She can look out for Brest tenderness, morning sickness this can happen any time of the day or night so look out for that, also frequent urination, missed period and last but not least moodiness.
Good Luck.
I guess she won't get pregnant. After all, you had sex during her period. The sperm's validity I think inside the woman's body is just a matter of hours, after that, it would just die naturally.