Your history is not enough to say about,
Weather she is having chronic cough
or breathing trouble of asthmatic type.
while playing she gets cough or change in her nails or normally color of her nails pink or blueish.
Any thing in nose like deviated nasal septum
or congestion on nose also can cause breathing problem.
if she is having anemia
then she may have this problem,
So better you consult your family doctor and seek his advise.