I went through this with my son when he was younger. Every cold he would get, the tail end, he would have this dry constant, constant cough..... I can remember calling the DR saying he was coughing every 3 seconds........ I get colds the same way!! The obvious things help, like humidifier and stuff like that. She is too young for stronger medicines, there is a good 12hr cough suppresant out there, but she is too young.
I highly reccommend you call your DR back, insist she be seen again and something be done for her. If it is this bad you post a question to us, then you need to call the DR. If he doesnt help, just go to the ER and they will do a nubulizer treatment right there........ We once had to do that.
Best of Luck ..... And Please, Please post and update on what you did and how she is doing....