Hi, I Just Want To Ask How Effective Nordette Because

Hi, i just want to ask how effective nordette because i came inside to my girlfriend during her 13th day ovulation. Her menstruation was jan 5 and we did it on the day of jan 19.We followed the instruction you gave that after we had sex she take 4 tablets and another 4 tablets at exact 12 hours. My sincere question is my girlfriend had bleeding discharge after 8 days Jan 27 that we had sex but supposed to be her period will be next month. Is this a chance of failure taking nordette and a sign of spotting that can cause early pregnancy? Or a hormonal disturbance or side effects of the drug? Please answer. Thank you!