If her period is late then she needs to take a pregnancy test.

Here is something I picked up.....


Side effects of Postinor-2 can include some nausea that may lead to vomiting, although most women experience only a short period of nausea after the first dose. Fatigue, dizziness, and tender breasts may also result from taking Postinor-2. Generally, these effects will be mild and will fade within a few days. In a very few women, the next period may be unusual. Any changes in menstrual bleeding, or increases in pain from the normal period should be reported to a doctor immediately.