Nebuliser vs Cough syrup. Her cough now?

My daughter is 3yrs 7 months old. She had viral fever, cough cold starting 15 days back. Cold & viral has gone in a weeks time. Her doc took all tests and as per her reports suggested its a viral infection only. Also her pedia. suggested montair lc kid 5ml daily for 2 months as a precaution as she catches cold infection very easily. Also nebuliser for her cough suggested. Is giving nebuliser for cough better than a cough syrup? She is having cough since past 15 days now. It seems subsiding with nebuliser but now with a one day break of no cough she had this cough episode in the morning, what should I do should I give her a syrup or nebuliser? In how many more days her cough will go away completely? What will montair lc kid syrup help in? Will it also help in her cough? Should i be worried for her cough now?