Or it might speed her up. Adderall is "speed," you know, but with a fancy name. Did your doctor tell you that Adderall is addictive? I would sooner stick a needle in my eye than give this dangerous drug to my child.
Good question. I would think that if the dose is too high that she might feel the effects. Doctors typically start new patients off on a lower dose and than wait for feed back before they continue. At any rate, it is important to be in communication with her doctor. Dosage does have a partial dependency on body weight. The lighter you are (all other things being equal) the more it might effect you. I would assume the doctor has taken that into consideration.
Other thoughts. If she is in relays or jumping events it might help with her concentration, possibly even with starts.
If the dosage is making a difference, than beside talking to your doctor - I would also discuss the possibility of doing something different the day of a meet. For example, don't take the extended release version.
You might also want to talk with her coach. I doubt that she is the first athlete in the school to be on meds.
If you feel like it, I would love to know how the meds do effect her.
Best wishes and may she have a great season!