Hey parent of your kid (you sound like a dad)
1 - you know your kid best. If she's your oldest, I'd suggest caution that you don't start drawing a line between her 5:20 and a full ride D1. Have fun.
Check out this girl who was a great hs athlete, and broke before she could graduate. She turned to her faith, but the loss was still real.
https://www.theodysseyonline.com/gods-strength-and-love-through-injuries
2 - understand that there is a genetic maxima. Your kid might be early to that maxima. Or not.
3 - I've got a kid who runs and does another sport. Both coaches suggest / request year round. We're resisting.
4 - our kids running coaches are all about stretching and not getting injured. They're wizards. We took it super easy, and even then my "2nd place is first loser" kid got slightly injured his freshman hs year. His teammate is sidelined due to grow plate issues due to running.
5 - Check this out by dr Andrews. He sees multi-multi sport kids getting trashed, by doing too much , too young. See #1, re your kid. That age, there are children and young adults at the same chronological age, but worlds apart.
http://www.orlandosentinel.com/get-healthy-orlando/os-james-andrews-florida-hospital-orlando-20160316-story.html
What we found as parents, is you can create opportunities. But you cannot create desire. Let your child guide you.
Have fun with the journey. It's cool that you have an 8th grader who's fast ish.
A dad