Wait until high school, if at all.
She's only in seventh grade... this doesn't guarantee that she'll start procrastinating, and there's no need for her to start stressing out this early. Middle school is pretty easy so hanging out with friends a lot is no big deal.
Plus, some people on this site blow things out of proportion (e.g. "omg I got a B+! am I set for community college?"). Just encourage her to keep her work up and remind her to keep her priorities straight, and she'll probably be fine