Um, tpen, I have no idea about the coughing thing, but I have to wonder if you're still looking for evidence that she's got addiction issues? Does it really matter if she's coughing when she gets out of the shower?
A friend of mine in recovery for 8 years was the first one to say to me, "How do you know when an alcoholic is lying? Their lips are moving."
You'll never get the truth and there's nothing you can do about it. Yup, hurts like hell. Worked well for me to tend to my pain in the most acute phases...and I still do. I cry about my A almost every day and yet at the same time I'm "getting a life". I have new friends through Alanon, and I feel good about myself for the first time in a very, very long time.
My advice is to stop thinking about her coughing or anything else she did in this relationship that has ended...it has absolutely nothing to do with you, and never will. Now you have a life to live, and you can make it everything you want it to be. You can be free of it all!
Hang in there, you're doing great with working to go NC! It won't hurt forever, but will comes in waves that are sometimes really intense--but they will pass. Breathe deep and take care of yourself,
posie