My friend drinks alcohol after work most days. Once she has a drink, she can't stop, but will usually end up going to bed after 6-7 drinks, more or less. She has tried to control her drinking and hasn't been successful .However, her life is not unmanageable.
Yet.
However, the odds are that it will become unmanageable at some point. Alcoholism is progressive. For years I drank several drinks at night after a hard days work to "relax" much like your friend. I was very successful in my career and nobody, not even my wife, knew the extent of my drinking.
But physically, my body was keeping score and after a few decades of this behavior, physically I was starting to get in trouble. The hangovers and shakes in the morning started to get progressively worse. But being the bright guy that I am, I figured out a solution. By washing down my Egg McMuffin with a couple of beers I could solve the shaking problem. But that put me another step closer to drinking around the clock.
I came pretty close to losing a bunch of stuff I cared about in life, before I was finally able to get sober. I am an alcoholic and I recognize myself in the behaviors you have used to describe your friend.