If she gets a fever again... take her back to the Doctor.
head colds, can cause chest infections/problems... because the mucous from post-nasal drip goes down the throat and can enter the lungs. That happened to me before... .and it developed into Bronchitis and then Pneumonia.
I have asthma.
The inhalers/nebulizer... will help with breathing and reducing the constriction/inflammation of the bronchial tubes. So this is important.
BUT bear in mind, that these inhalers do not lessen mucous... it helps the airways and breathing. That is the purpose of it. It is not an 'expectorant' nor a mucous reducer.
Coughing originates from 2 sources:
1) the post-nasal drip.... because as it drips down the throat, it irritates the throat and causes 'coughing.' Triggering the coughing reflex.
2) the chest.... when there is a chest cold/infection and congestion.
Kids this age, do not know how to 'spit' out mucous. Nor successfully.
Is her sinus infection gone?
Sinus infections can take time to go away, completely.
If she is getting worse... you take her back to the Doctor or ER. And certainly is she gets a fever, again... or other symptoms.
Did they listen to her chest?
Give her water to loosen the mucous. Do NOT give orange juice because this creates mucous.
all the best,