If this was a cough that had been hanging around for awhile and seems to occur a lot after she get's sick then I would take her to a GP.

In my case my DS would always have a lingering cough after getting a simple runny nose. We tried AB's which had no effect and then we tried asthma medication. DS now is on a tablet he takes daily which is the prevantitive and we had to use ventolin this time after he got a cold to get the cough under control. The only other symptons he had that indicated asthma (albiet a mild form) was that he would cough a lot in cold air and if running around a lot (as well as coughing a lot at night)

Anyway goodluck and hope the cough goes away quickly.