Does Intake Of EC Pill Lead To Breakthrough Bleeding?

My girlfriend and I had protected sex on more than one occasion, the condoms did not pop, burst, tear, fall off, leak or anything and I used the pull out method to be extra sure. She was worried about getting pregnant so she took an EC pill twice but a few days apart as she didn t have her renewed prescription, a few days later (now) she has what I think is breakthrough bleeding. What are the chances of her being pregnant and is this bleeding because of irregular first time use of pill