Good for her!
There is nothing that you can control, so relax and enjoy the ride!
If you are concerned about her getting knocked up, you need to talk to her about it and find out her feelings about becoming pregnant and having a bi-racial baby. This needs to be a serious discussion as she needs to really contemplate the issues that would affect not only you and herself, but more importantly, what would be best for the baby. Unless both of you are truly desirous of raising a baby and prepared to accept all of the challenges, she needs to get on birth control ASAP!