Hi.. There are chances of pregnancy.. However  there are more chances that it can be the one of the side effects of the birth control pills that is causing the delay.. But if she develops any other symptoms of pregnancy such as nausea, vomiting, enlargement of breast with or without soreness, food cravings, mood alteration or any other symptoms, then you have to take pregnancy as a strong possibilty.. And if you wish that you do not intend to wait for such a long, you may take the test for pregnancy.. Bear in mind that birth control test can alter the findings of pregnancy test...