I agree that finding boys and body changes are factors that can ruin a great girl runner, but I think there are other things that are much worse. I am APALLED at how terrible coaching is for women in college.
Somewhere it has been decided that girls need to do tons of General Fitness Exercises (GFE). It is like taking a race horse out to plow the field before a big race. And weight training; My gawd, why would anyone who wants to run a super race spend good running time on weights?
Distance runners (800 & up) need to develop a very special type of muscle structure. It is a long, tempo-firing endurance muscle. Weight training and GFE build short one-time firing muscle; just the opposite of what a girl needs to run well.
And, most of the girls who run so well in high school just go out and run. They take off hard, run from the heart, get away from everyone except perhaps the toughest, fastest, competitors, and then keep going. When they get to college they run into some boob-head of a coach who immediately trys to CHANGE THEIR RUNNING STYLE to be a wait-and-kick style runner, like the coach read about in the coaching book he/she read. GONE is the heart that got the girl where she was. Maybe one year the girl runs well, and then she falls apart.
Touch-and-go-bullit-head coach sees the girl fall apart and ASSUMES it is because of life changes or a boyfriend. It isn't! It is because girls get terrible coaching, even in the biggest of schools.
If you can find a college coach who encourages a girl rather than try to analysize her form/style/speed, please tell everyone that coaches like that are out there. Most of them are egotistical, arrogant, self-centered fools who are only interested in making sure they don't get fired.
I tried to build a great program in a DI college only to be strapped with a head coach who insisted on GFE twice a week. She worked those poor girls so hard in the pool it took me two days to get them back to zero again. She had read about those drills in some stupid book and KNEW all girls need that. When finally I got them all away from GFE workouts EVERY GIRL I COACHED hit personal best performances. Every girl! That prompted the head coach to step in and TAKE OVER! No more personal bests; lots of GFE and no more heart running.