I don't think she is. Her father was and she's afraid of becoming one. The alcohol in her डेस्क was tequila. Her and bosco used to take टकीला shots when they closed a case.
I don't think Lisbon is an alcoholic because we have never seen her drunk. Most alcoholics are drunk for a good bit of the time, and we have never seen Lisbon drunk. Who knows, maybe she wasn't trying to hide the alcohal in her desk, maybe she just has a shot once they close a case. It never implied that she was trying to hide it. I think if she was, we would know and not have to guess.