my quit smoking councelor (spelling?) informed me that coughing in the beginning of a quit is normal. Some people start coughing the first week while some don't start until the second or third week into a quit. It is the "little hairs" in the "air tubes" (trying not to sound too medical) that are awaking back up. This is common with any type of quit from analogs (especially cigarettes).
That was my first big quit - before I decided to do the vaping. I was quit for almost 6 months and coughed a lot near the beginning (half way through the first week and on through the fourth week). I was told, take ice chips and let them melt to help keep my throat wet to help with the cough and take a honey cough drop (because it does not contain any medicines) to help sooth the cough if it became too hard. I was also told not to drink anything with caffein (it would dry up my throat as well), not to drink any citrus juices (orange juice, pineapple juice, etc..) cuz it can also make the coughing difficult. If nothing worked or if the cough was the normal "smoker's cough" which is very dry and hard and of course if my asthma started acting up/difficult breathing to consult with my doctor about it.
If your wife is coughing and has mucos (sp??) or flem coming up, as long as it does not look like an infection then it is a very good sign. That is the "hairs" waking up and also the lungs expelling a lot of the nasty garbage from the lungs. You won't have that cough mainly because you didn't smoke and your "hairs in the air tubes" are not "sleeping" and you also do not have a lot of the nasty stuff in the lungs.
congrats to her for quitting smoking, let her know she will get through the coughs and help her when you can. Soon, she will breath better at night and be capable of breathing much better with less if any coughing at all.
That's funny! Hey, yah, you're not supposed to vape if you're a non-smoker! Vaping is for smokers who are trying to quit! ...yadda, yadda, yadda! 
