Poor little poppet It is so heartbreaking listening to them cough.
I don't use cough medicines for my kids at all, especially for asthma as I feel they don't work.
If it is a dry asthma cough then I find ventolin seems to really help...say something like 2-4 puffs with 4 breaths each puff...if you have ventolin and the predimix.
If it is a mucusy cough you are better of letting them cough up as much as possible to get it of there chest, things like sitting in a steaming bathroom, vaporiser with eucalypt, laying them over your knees and tapping their upper back to break up flem, raising the end of the cot may help.
I hope the coughs eases for her soon