What Causes Prolonged Periods After Taking Unwanted 72?

Well, my girlfriend took an unwanted 72 tablet after making out which involved my penis touching her outside of vagina...
after a week of taking the medicine, she started having her periods which just doesnt seem to end. Its been 15 days today and they are still heavy. This has never happened before. Can you please tell us the reason for it and how it can stop..