Lets get something clear.  Best friends DONT have sex.  Friendship is not sexual. People dont have sex with their friends.  If there is sex, thats not a friendship.  If its sexual, it is a courtship and dating.  Secondly in a sex game anything goes...  like the saying  "EVERYTHING IS FAIR IN LOVE AND WAR"  If you have a sexual crush, then pursue her as hard as you can, relentlessly just like any guy who wants a girl will do.  She likes to play the head game, the sexual tension, leading people on. If she cared for you as a friend, she would not play games. You better move on,  she may run after you after you are gone. But when you walk away, dont fall for the games no more.