How Long Does Postinor Stay In The System?

How long does the Postinor 2 remain in your system for? A friend of mine took the pill because she has Fibroids and did not want to be pregnant before she visited the gynae one last time before she tries, now she is ready to try again but concerned that the pill may still be in her system. She took the pill on Friday, January 30 & 31, 2015. How soon can she try to get pregnant? Her next gynae visit is next month end hence the reason she is asking. I m curious myself.