Thanks for the query.
Emergency pills can give protection up to 24 hours after completing the course.
But sometimes this may not happen.
According to the history the chances of pregnancy
Anyhow you wait till her expected date of periods.
And if she miss the periods, go for pregnancy test once.
If the test comes negative you can wait for one more week, possibly by that time she will get the periods.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429