I personally wouldn't tell the parents of the other girls especially if you don't know them that well ... and it could come back on your Daughter ... Which would then leave these popular/powerful girls falling out with her and probably making her life a misery ... If your daughter felt uncomfortable with the sneaking out/drinking/drugs ... Maybe she could just phase herself out of that group ... Just start hanging about with them less and start hanging about with other girls more? That way it would probably result in no hard feelings towards her for not hanging about with them. Or she could just start declining their sleepover invitations ... they will soon get bored of asking her?
Surprised no one has replied. You know the old saw about shooting the messenger, yeah? That's what would put me off trying to tell the other parents. I am wondering if you could productively inform the school.