A cough that has been going on for a few months and gets better without talking

My mom has this cough that first appeared in early July. It started out as an occasional dry cough, but since then has developed into a severe cough with phlegm. At this point, she can barely finish a sentence without coughing. I was away for one weekend, so she was home alone. She had no need to talk, so when I got back her cough sounded better. Back at stage one. Since then, it has gotten worse than it ever was.

So bottom line, she can rarely finish a sentence without a coughing fit.

Note: She is a smoker, and has been for about 11 years.