Isn’t this a slippery slope?

Not sure where to post this but thought this would be best.

My dad is a recovered drug addict and he is married to a recovered addict as well. But I noticed since thanksgiving that she drinks. And I see her posting stuff and tagging my dad in stuff about alcohol on Facebook. Is it possible to control the drinking and keep it at just a drink here and there or is it a path right into addiction again ?