Taken Norifam To Prevent Pregnancy. No Periods. Worried

Hello, my girlfriend took Norifam to prevent pregnancy. she s supposed to have it injected on the 1st day of her period but instead, she had it on the last day. I figured the reason for having it on the first day of her period is to make sure she s not pregnant. By then we never had contact from her first day to the last, so I was sure that she wasn t pregnant. I read that users usually have periods 2 weeks after the injection however she hasn t. I m just worried because it s been 3 weeks and she still haven t had that supposed menstruation after the injection. Could she be pregnant? Or is there even a possibility that she could be pregnant considering that she had Norifam?