According to her LMP, expected due date was around 25th-27th February in case of 28-30 days cycle. You did sex on her fertile days (7th-15th Feb) and pull out method has high failure rate (15-28%).
Taking I-pill after 28 hrs of sex gives protection only 85%. In case of of failure of I-pill, she may become pregnant.
Another thing, 1-7 days period due date alteration is normal thing and mostly due to stress
imbalance. Therefore, if her periods are delayed by more than a week, she should go in for a pregnancy
test and contact her doctor for suggestive measures.
Try to avoid stress by yoga/ deep breathing, take healthy diet and sound sleep. Practice safe sex
in future to avoid unwanted pregnancy.