This is soooo easy man. Plug as much as you can in highschool or you will regret it!
Hook up with wendy, youre friend will get mad at her not you, usually happens like that. Then that gal sall will resent you for about a week but after that apologize gifts etc. you should know the proper way to make up with a girl if your asking this. Then act like you never knew she had feelings for you and say you'de be willing to explore them further with her. Have at least 2 months of plugging and try to meet as much of her friends as possible and become close with them to open more options in your future once sally is used like a 96 civic. Have fun.
I know this will work. Sally won't realize she has feelings for you untill your with another girl. Or she never liked you and you keep stickin it down wendys throat.