Aside from the standard 1 percent what is the chance of becoming pregnant if you miss a couple days of your birth control medication then have unprotected sex after 4 days of taking it as prescribed?

You should take other precautions for seven days after missing a pill. If she missed three in a row I would say there is a pretty good chance she will ovulate. Whether she will fall pregnant - there is a slight risk. Remember the pill stops pregnancy in two ways - firstly stopping the egg being released and secondly by stopping the fertilised egg implanting into the uterus lining. Ask your g'f to take a morning after pill just to be safe.