I ran cross country in college. Those were 5 mile races and would kick your ass. Guys would run them in the very low 20-something minutes (~22 minutes). If you did not run under 24 minutes, you were hopelessly behind everyone else.
Those are my only qualifications.
Speed training - Teach her to run one mile in 6 minutes or less (75 second laps around a track, 4 times).
She will learn what the pace feels like and she will build the lungs and legs for it.
If you're coaching her. Keep her split times.
Warm up.
Run the one mile.
Rest & recover.
Run one mile again.
Rest & recover.
Do it again.
Rest up a bit.
Do some cool down and stretching, then go home.
Don't kill the kid, especially at the beginning of training. Let her work up to it.
Even so, she has to be able to run a mile in the 6 minutes, at least one time, even if it is only one lap at 75 seconds to start with, then two laps, then 3, then the full mile in 6 minutes.
Fartlek Training - lots of videos on this, look it up.
That's what I know. That's all I know.
Cross country can be fun because the courses vary so much and are not traditional, circular tracks.