Her body is not a machine that does the same thing over and over. Her hormones can be disturbed, or she can be worried and stresse. It can all cause irregularity.
A normal cycle is between 21 and 35 days long, with the average around 28 days. Something like Plan B or i-pill can disturb that. So from the 5th of February until March 1 is 26 days. It is quite a normal cycle.
It does sound like she has a history of irregular cycles. She should write the dates down and speak to her doctor if she is bothered by it. Depending on her age, it might not be a problem. It might also take a while for her body to become regular again after the i-pill.