unfortunately, this is America and it's 2008. She doesn't have to worry about much of anything except staying HOT.
When this slug is gone, there will be a big line new slugs ready and willing to pick up the pieces.
Isn't she also the girl who got to do some modeling? A great opportunity, yes; but not the best lesson for "hard work = reward".
I think you HAVE TO remove some freedom or privileges, and help her realize that the good grades = freedom, (like so many guys already said.)
And remember, it's quite likely I have absolutely no idea what I"m talking about.