Emergency contraception pills are around 98-99% effective if taken within the first day. So she should be fine. I will warn you, and have you warn her, they can have nasty side effects. Don't be alarmed if she has cramps, nausea, dizziness, headaches, bloating, fatigue, bowel irregularities, is late on her period, spots randomly, has an excessively long period, or has appetite change.