Is There Something To Worry If Period Is 1 Day Late?

My girlfriend and I had a condom break a week and a half ago. She is on birth control pills, and takes them every night a 9pm. she had missed a pill 3 days earlier but caught up, she had not yet taken her pill when the condom broke. She took Plan B emergency contraceptive within 3 hours as an additional precaution. Her period is 1 day late, is there really any reason to worry about pregnancy?