It is good to have concern for your fellow runners. Let me see if I can help you. Why in particular are you concerned about with this young lady?
Let me ask a few important questions that you will need to know the answer to in order to determine if there is cause to be concerned.
1. How long has she been running?
2. Has her training been consient during this time?
3. What has her training progression looked like over this time?
4. Do she like what she is doing or is she being forced or coaxed into running this much?
5. What does her training week look like?
6. Does she run at home or have to travel to a team practices
7. Who is her coach and what experience/expertise does he/she have?
8. Is she underweight or just runner skinny.
9. Does she have any eating problem?
10. Does she get the proper nutrition/supplements for someone doing that mileage?
11. Are their any problems she has experienced with growth or injuries?
12. What running events is she interested in pursuing?
While its good to have a healthy concern for other runners, especially kids, it can be very hard to make judgements that there is a problem without knowing the answers to questions like these. If there is numerous evident problems or even one large obvious problem outwardly apparent than your concern may be justified.
But don't fall into the trap so many do and just assume that because something is unusual that its bad for everyone. Don't let limited frame of reference sway you into making snap judgements as so many do.
If you know the answer to the above questions (or even some of them) let us know and we can help you decide if there if cause for concern.
All of the pediatricians and sports doctors I have talked to have told me that it's fine for kids to run a good abount of mileage as long as they enjoy it (i.e not forced), have built up to it slowly and don't have nutritional deficencies. After all isn't that how so many young Kenyans got started.
Best,
MPR