Generally, once you're over the contagious stage (usually about 3-4 days), the cough that's left is a result of the bronchial irritation, and not infection. Yes, the lingering cough can be annoying, and it can take up to a month to go away, but no one can afford to stay home that long. Princess co-worker needs to suck it up and wear earplugs if it's that annoying. OP is doing everything possible to alleviate the situation.

Wow...what a useful idea. I'm sure op hadn't thought about that.

they did say they RETURNED to work after a bout of sickness, meaning they had already had sick days. and after having a respiratory sickness, you can feel and be better, but the cough can stick around for however long it wants, without being infectious.

I pray that's a comment full of sarcasm!

Somewhat a mix of sarcasm and truth :P Quite shocked it's not been buried! We all know listening to somebody constantly coughing does get very annoying though, no matter how much they can't help it!

I was looking for someone who'd say this. If someone is ill in class and coughs for hours, that is really irritating. I understand you're ill, but please stay home, don't spread it and let other people work. If, despite all OP did, the coughing was still so frequent, OP should have stayed home.

Op took sick days. Companies get cranky and fire if too many are taken. After a few days, most if the time you are no longer contagious. So it's a sucky situation all around. But it's not selfish to return to work when you are better. Coughs can linger. I had one from a bout of bronchitis that stuck around for three months. I'm sure my coworkers were not thrilled having to listen to it. I went to the bathroom if it got bad. But I couldn't miss three months from work when I wasn't sick just because I had a lingering cough. You do what you can to make the best of it and hope your coworkers will show understanding. And you give your coworkers that same understanding when they are in that position.