This is most likely to be an respiratory tract
infection which is common in children of your daughter's age. It is caused by a virus and is usually self-limiting and will gradually get better over the next few days. She may benefit from some Paracetamol
which will reduce her fever
and help with any aches and pains that are common with this type of virus infection. Keep her well hydrated by encouraging her to drink plenty. Her breathing may be helped by steam so letting her sit in a steam-filled bathroom is worth trying. She may not sleep very well whilst her breathing is heavy but these simple measures are likely to help.