OP wants to have his cake and eat it too.
He wants to report his sister so that she will stop drinking
He also wants to do this anonymously so that she will still like him
1) Reporting her "anonymously" is stupid. She will know it was him in various different ways.
2) Reporting his sister to the police will put her on record and "on the list", possibly put her in rehab stuff, ruin her social life, possible give her depression, ect.
It isn't so minor. She's at the stage where she is still learning right from wrong, she's still forming her brain. She is going end up growing up thinking that it's a little thing to steal wine, then it's a little thing to steal money.... Get the dilemma? While her addiction is low, she can stop it now. If not, it'll probably end up worse.
That's not how it works? She
knows its wrong to steal wine and to drink alcohol, but that is part of the reason why she is doing it lol.
https://www.youtube.com/watch?v=ZbdMMI6ty0oPart of the video explains why we like doing things we aren't supposed to do/like.