Messing up birth control and pregnancy.?

A friend of mine is a little worried about being pregnant. She is 29 years old, she called me and ask what I thought of the situation. She said she missed 3 to 5 pills and had . She said when she does miss she always haves break through bleeding. This time she has been off the pill for almost 3 weeks and no sign of blood not even break through bleeding. I told her she very well could be, but I haven't been on birth control for 10 years and when I was I only took it a month, due to making me so sick. Has anyone missed pills and got pregnant right away. Or do you think I should tell her she could be fine. She is taking a test tomorrow, but she still calls me so worried.