A fever, cold, and cough lasting many days in a young child are usually due to a lingering infection or a recurrent viral illness. Give plenty of fluids, keep her warm, use saline drops in her nose, and ensure proper rest to help with recovery. Offer light food, maintain hygiene, and watch for signs such as rapid breathing, poor feeding, or a high fever. If it lasts for many days or does not improve, consult a doctor to check the cause and guide proper treatment.