If it is a cold, symptoms will generally get better in 7 days or so. Usually cold is worse first couple days then slowly gets better and peters out.
If symptoms linger, get worse not better, cough keeps her up at night, decrease appetite, fever, set me on high alert for a more bacterial type of thing. I do the same as Liza, up treatments, push fluids, and call the doc depending on her last culture will depend on which antibiotic she needs.