Hmmm. Seems like she might have her own issues with alcohol? I'd tell her, especially since it's on your FB - it's fair game once it's on FB as far as I'm concerned.
Or you could just delete the post if you really don't feel like talking to her about it.
This is one of those things that there's no right or wrong answer for - it's your sobriety and entirely up to you who you talk to about it.