Should i do cross country or volleyball?

I had the same problem as you have only instead of volleyball it was basketball ( I'm a boy btw). I didn't exactly sucked at basketball but the problem I had was that my team was so good that I was always in the bench but other than that when I played in other leagues I could dunk, shoot, dribble the ball in an elite way but still I wasn't as good as I was in basketball than what I am in xc\track so I decided to part my ways with basketball in order to improve xc and track. It was really hard and depressing but it was worth it because at the end I was able to focus more on track by entering a track club and I eventually got my times lowered dramatically (Even injured). My tip? do whatever you want.. If you want volleyball because you love that sport and because all your friends are on the team then join the team and if you want to run then run. And by the way if you can run 7 miles nonstop you're probably gonna have a good xc season an your mile is actually a good time for your age. (Sorry if there's any grammatical error, English is not my first language) hope I helped in any way