Pill, Pregnancy Question

Hey me and my gf were having sex...Usually with a condom but a couple times we had unprotected sex just for a real short time and I pulled out before I cummed. I know that precum could get her pregnant. The thing is that she is on ortho tricyclen birth control. However, she had missed taking it for two days and then took an extra amount the following day. Could missing it for two days make it possible for her to get pregnant? Any help would be greatly greatly appreciated. Thanks!