Birth Control question! Please Help!?

My fiance has been on BeYaz Birth Control for over a Year and is religious on taking them on time. A few nights ago I came inside her I have never done it and we wanted to try it once. Well shes getting nervous about it and I was curious to see what the chances of her becoming pregnant are. Are we safe? And yes I know BC is not 100% and no she hasnt taken any antibiotics and yes she has taken them on time and hasnt missed a pill. My question is do you think we are safe? Should we be worrying?