At least with Snapchat the pics won't stay up, and she can always remove the Instagram ones later on. I think it might do her good to see them
Snooz...
I don't think many parents would put up with this behaviour any longer, obviously it's very dangerous for her, and it's not fair to the rest of the family. If she is having trouble with her drinking love, you are the very best person to help her. If it was me, I would give her a few choices...and hopefully she will hear you.