It can be really difficult since as parents, we worry about our children. Doctors and nurses take a more realistic approach I guess, and can tell when a child is really ill. As for pneumonia, she will have a very high temperature and become quite listless with her breathing fairly labored, so I wouldn't worry to much about that at present. If the cough sounds dry then I suggest a vaporizer of some type. You can use these with just water, or you can add drops which help to ease breathing. A dry cough is generally caused by dry air and the cough can really sound awful.

There is one thing I can say, your kids are often the best guide when it comes to illnesses. If she is happy, eating well, then don't worry too much. Add some moisture to the air and let it run its course. Whatever you do, don't start sterilizing everything - read these posts first - Are We Becoming Too Clean and Cleanliness v Sterilizing

Let me know what happens :)

Les