Hello, First of all, pregnancy depends on proper timing of unprotected sex with ejaculation and ovulation time. Sexual activity 4 days before period due date is quite safe. Here, chance of being pregnant is quite less. In general, period may be delayed up to 7 days due to hormonal imbalance and stress. She can wait 7 days to get period normally. After that, she needs to undergo one home pregnancy test to rule out pregnancy. Following test report, you can consult with gynecologist for next management. On positive test, medical abortion should be done under supervision of doctor. Practice safe sex in future. Good luck.