No she can not. The test will not be accurate until at least 2 weeks after sex. The egg might be fertilized after 72 hours but it takes a week to travel down to the uterus and get attached.
What is 72 hrs from yesterday, Thursday 10am?
No
72 hrs
72 hrs.
72 hrs
No
72 hrs.
Saturday 1pm.
72 hrs
72 hrs
72 hrs
72 hours * 1day/24 hours = 3 days