How do you offer relief to a child who has asthma and a cold?

My daughter is 2 and was dx w/asthma at 1 year.  Her asthma is only brought on by respiratory infections and colds.  She takes Zyrtec, 2 neb Pulmicort tx, Albuterol neb tx when needed and Singulair every night.  She currently has a cold with a runny nose and sore throat.  She also coughs violently all night long.  What can I give her or do to make her more comfortable and able to sleep through the night?  I'm guessing her cough is worsened due to post nasal drip as there is no mucous coming up when she coughs.  I currently have a warm mist humidifier in her room and have elevated her mattress.  Nothing is working.