Hello and thanks you for using HCM.I carefully read your question and I understand your concern.You shoud not worry about this. I will try to explain you something and give you my opinion.
Causes of shortness of breathing in young ages are usaly related whith strees and not a serious problem.
Stress,excessive coffee consumption sometimes might cause
sinus tachycardia,extra sistolic beats that are manifested whith
anxiety sensation, shortness of breath.
Pathologys like
anemia ,
hyperthyroidism might also cause the same simptoms.
In my opinion, as she is very young this is nothing to worry about. It will soon pass. But if this realy bother her than we can decide to do some examination.
If I was the treating doctor I will recommend an electrocardiogram, a cardiac echo to evaluate heart function, a full blood analyze , thyroid hormones and a holter rhythm monitoring to see what happens to her rhythm during this symtoms.
Hope I was helpful.
Best regards.