While everyone is preparing to light torches and gather pitchforks, you might want to take another look at the whole thing without getting in an uproar over the term "slut" and "tramp."
Those of you that take offense because what she does is "similar" to
stuff you like to do...do you think it's responsible behavior for a
parent to come home drunk in front of their kids? Do you think it's
okay for a parent to threaten to never bring her kids over to visit
their grandparents again because they disapprove of this?
The grandmother didn't directly call her child a slut or a tramp (even if she felt the behavior was such), she simply told her that if she planned on staying out drinking most of the night and coming back drunk, she should stay in a hotel. That is perfectly reasonable. If the woman wants to stay at her mother's and have free babysitting for the weekend so she can go "play", I'd think it's reasonable for it to be on her mother's terms.
Prudie's response might be a little harsh to you, but she's usually direct in her responses. But her advice in "your child is acting like a child, and you have a right to not indulge her behavior in your house" is spot on.