What Causes Vomiting While Coughing At Night?

Hello, my 2 1/2 old caught a cold about 2 weeks ago, to this date, she still has stuffy nose and minor coughs. a few days after catching the cold, she started to vomit when she coughs really hard. on an average, she vomited 2 to 3 times a day. About a week ago, she stared to vomit only at night, about two hours after she went to bed. The first few nights, she would vomit after coughing a lot, but the past few nights, it seems that as soon as she coughs, she vomits. She appears to be alright during the day. what can/should i do?