Try cutting some carrotts into slices (still with the skin) and pop them in a bowl then cover the carrotts with brown sugar so that you have a nice coat of sugar on top on the carrotts almost covering them... Cover the bowl with a kitchen towel and leave over night by a window, in the morning you will have a syrup give it to your daughter when the cough gets really bad. Because there is no chemicals you can give it to her as many times a day as it needs and she will like it as it's sweet :)
My Nan used this on us all the time and it worked, untill today it's the only things that sorts out my chesty dry cough even with a chest ot throat infection...
Give it a shot...