I would suggest:
Fluids. Keep her well hydrated is vital, you should give plenty of fluids like Pedialyte and juices and milk along with feeds..
Otrivin Saline. nose drop - to keep the nose open - one drop in both nostrils three times daily.
Cough syrup like Benadryl DR: Discuss with the pharmacist about an appropriate cough syrup for him. As she is above 6 years, you can give him a cough syrup like Benadryl DR which works in dry cough.
Humidifier: use a humidifier in your room at night as dry air aggravates these symptoms.
Use a neck wrap or muffler to keep the throat warm
Another important home treatment is Menthol steam inhalation - add Menthol salts (available OTC) to a bowl of steaming water and inhale the steam two - three times daily - this will relieve the congestion.
Logenges: suck hard logenges like Vicks cough logenges or any hard sweets constantly, this will cause a constant flow of saliva and give you relief.
Hope I have been able to clarify the situation for you and helped in resolving your query.
If you need more help, please let me know so l can continue to assist you.
Thank you and I wish you the best of health - stay safe!
Dr. P. Jyoti