Is There Any Side Effect For Taking Plan B Tablet?

Hello, my girlfriend and I had safe sex 5 days ago but we did a bit of fore-play and were afraid of pre-cum impregnating her so we bought plan-b. She took it within 8 hours of intercouse and 12 hours after as directed. Today, 5 days later, we had anal sex and again were afraid of pre-cum. So we took it again. During the first session a condom was used but the second there was no condom.

What happens with taking the plan-b dosage twice in one week?