Does Intake Of Nordette Post Unprotected Sex Help To Avoid Pregnancy?

Hi Doc, my girlfriend and I had unprotected sex 2 A.M on January 17, 2015. She had her period on January 3, so we presume she was fertile following the 28 day ruling but her menstruation is irregular. So do we still follow the average 28 day fertility scheme? Was she fertile at the time? She took 4 pills of Nordette-21 36 hours after the deed and 4 more twelve hours after. Is this still effective?