hi,thanks for query.Please understand that if she has missed periods please go for urine pregnancy
test to confirm.Wait for her to miss period,at times some form of anxiety
or any pills taken can lead to delay in periods.In case the test is negative please ask her to see her primary care
physician and take some tablets which will lead to periods.I hope as you done sex in the beginning of cycle and end of cycle the chances of pregnancy are less.Please take care and avoid this risky behavior as you still teens.Precaution is must of all.
wishing you good health.