The fact that she broke a school record in a sprint does not mean that much unless your school has an incredible record. Many people do not realize how many great runners there are in America. I used to think that running under 2:00 in the 800 was special for a high school boy. There are literally thousands of boys who can run under 2 minutes in the half. (LRC doubters look it up for each state on Milesplit.com!)
In training the easiest thing to increase is strength, the second easiest is endurance and the hardest thing to build is speed. But it can be improved if it is worked at every week doing 5 X 70s, short uphills, downhills, bounding uphills, rope skipping, fast dynamic running drills, form work, plyometrics and etc. To get fast you have to run fast in practice!
Perhaps the best thing she could do is get a sprint coach for the fall and winter (never run sprints outdoors when it's below 50 degrees!).
She might be motivated if she can work at what she is good at. I'm not sure that running cc will help her sprint better. The only way that would be true is if she is the type who sits around all fall and winter. Another option is for her to play lots of basketball and volleyball although I do not like the sprained ankles in those sports. Perhaps she could just play a few minutes of that daily.
It's possible that she could be better at long distances but you did not give us a time to go by in her sprint record so it's hard for us to judge. It is true that some people cannot be distance running greats and can only be good at sprinting! She may suspect this and thus is not encouraged to try.
If you cannot get her with a sprint coach perhaps she can get with some of her track & field sprinter teammates and workout this summer. Sprinting does take work but it's more technical that distance running. They must learn acceleration, the classic running form, and starting techniques. Perhaps they could get into watching You Tube.com videos and teach themselves. If inspired...they will do it!!!