It is unlikely that she is pregnant as the effect of the pills last for about 96 hours. Although there are a few (1%) cases of pill failure that you need to be wary of.
Emergency contraception -- also called post coital contraception -- is a form of birth control that may be used by women who have had unprotected sex or used a contraceptive method that failed. Emergency contraception is not a form of abortion; it is used to prevent a pregnancy, not end one. Emergency contraception does not protect against sexually transmitted diseases.
I would recommend the following-
1)Take another urine pregnancy test to confirm that you are not pregnant. It may also help, if you are very anxious, to take an ultrasonography of abdomen.
2)Don't take more than one kind of emergency contraceptive. The active ingredient in one agent may counteract the effect of levonorgestrol.
3)Don't take extra pills. They will only increase the chances of side effects like soreness of breasts and vomiting.
4)Eat a good balanced diet with good portion of proteins carbohydrates and vitamins. Consume diet rich in green leafy vegetables and milk. This will help in improving the immunity of the body.
5)If you have any other symptoms you are worried about like extreme leg pain , nausea and vomiting.