If she is over 18, hopefully she has enough sense to understand that a nasty breakup and family finding out would only hurt the family and will handle things like an adult. You need to explain that although u like the sex, a relationship would never work due to your close kinship. When you are in a relationship, especially if the L word is involved you normally want the world to know about it, but in this case neither of you can let the cat out of the bag because of the reaction it would cause. does she, or you for that matter, want to live a seceret life that will just cause you to be unhappy about it in the end?
If she is under 18....your screwed. can't dump her cause she would squeal, can't keep her because, well eventually she will squeal. Even if you wait till she is over 18 to dump her, she can still have you brought up on charges if she wants. In most states that is.
Your best bet is to give her a reason to break up with you, without making it a harmful, nasty breakup such as getting caught cheating on her. No what you need to do is things like whater she is into, you are the opposite. If she likes country, fuck that you like metal. If she likes quiet times alone, you like going out late partying, and make sure to drag her along so she is miseriable. You have to become so incompatiable she will not want to be in a relationship with you.
