Many people in many different countries find sexual attraction to ones cousins taboo. Keep this in mind as your cousin may share this feeling.
Right now your cousin is 17 and is under age in most parts of the U.S. So ensure that by you and her having a relationship you are not doing anything illegal. If she is considered under age her parents may pursue sexual assault charges on you. It might look worse to her parents and the criminal justice system because you are her cousin.
Also remember that in many states in the U.S. You cannot marry your cousin. To what degree cousins can marry varies widely from state to state so you might want to check that out as well.
Many children born from parents who are closely related have many problems. This includes increased risk of miscarriage, birth defects, genetic defects, and low IQ.