as you had intercourse around the time of ovulation there is more possibility for fertilization, the pill will usually prevent pregnancy
but there is some amount of failure rate for the pill and also sometimes urine pregnancy test kits can give false positive results,
you should not take any tablets for abortion
without consulting doctor and excluding ectopic pregnancy,
so let her consult gynecologist once and undergo ultrasound
which can confirm intrauterine pregnancy and rule out ectopic pregnancy then with your doctor's advice she can go for tablets.