D.B.
Elevate the head end of the mattress by putting a folded blanket underneath. She'll sleep at an angle and sometimes that lessens the coughing.
I always had bad bronchitis with every cold until I added the proper, balanced, nutritional supplement with everything in one formula. Powder mixed in liquid, no pills, nothing pre-mixed. I learned about it from a sports professional and his teacher wife whose child had pneumonia-like symptoms 3 weeks out of 4 for the 2nd year of his life. Changed their lives. It's not a quick fix for the existing problem, but it supports the immune system so it doesn't happen again. Prevention is better than treating symptoms after the problem develops, you know?
Good luck - I hope you get some sleep!