I took cocaine when I was younger (early 20's) and I was able to just walk away from it. I look back on it and see how it could have gone bad real easy. Cocaine is a very dangerous habit and a lot of people don't just walk away from it. I was lucky.
I know plenty of people who used cocaine recreationally and grew out of it. Not everyone does, some develop real problems, some lose their lives.
Either way, there is probably not a damn thing you can do to discourage someone from taking drugs. You can be there for them if they ask for help.
You can only captain your own soul. Just be a friend and live your own life.
Everything may APPEAR good,but regardless of how good things look sooner or later somethings gonna give.And/or does everything look good as seen through the cocaine haze?