I hate to say it, but your friend might have a mild case of COPD or other problem that was "ignored" before now. I know I coughed like a son of a gun when I first switched over... had to take itty bitty puffs, hold it, let a bit out, inhale, then exhale. But I worked it baby and it didn't take long before I could handle an almost normal puff. A week or so after that I noticed my nightly wheezing had stopped, I could walk up hill without having to stop to rest as often, and so much more.
It wouldn't hurt to get checked... besides that, the health improvements will be "officially on record" too.
Lots of ex-smokers with COPD are now appointment free, with shocked Dr.'s fainted on floors.
Stopping the smoking is paramount and if Vaping is the only way that it can be conquered, then don't give up!