High functioning alcoholic 

An excuse term alcoholics use to justify their continued self-destruction.

Joe: "Wow, James is drinking and it's only 7 AM."
Mike: "He's a high functioning alcoholic. He says he needs it to function."
Joe: "So he's a severe alcoholic who needs help then."

High functioning alcoholic by Super Thicc November 22, 2020

High functioning alcoholic 

Someone who always drinks too much and whose life is falling apart because of it. ... Some people seem to be just fine even though they abuse alcohol. Experts call these people “functional” or “high-functioning" alcoholics."

Even though we never see Sarah sober, it doesn't get in the way of her life.

Sarah being a high functioning alcoholic has a sucessful life, job, and family.

High functioning alcoholic by Kenztenz July 30, 2017