(Wow, this got dark...but it evolved naturally...)
Unpopularity seems easy, but it's a very strange thing...hard to define and harder to explain. If the school and among the girls who had been her friends she vanished, a stranger...and an unliked on at that. But the REAL changes...were going on downstairs. Her parents suddenly stopped thinking about their daughter as their "little princess" and instead as "the brat". They thought of her as a tiresome snot who was a drain on their patience and finances. Instead, they suddenly turned their attention to their own relationship. They'd never wanted a child anyway, and they only tolarated her presence as long as they had to. Once she turned 18, she'd be out the door.
And so, as they were unwilling to squander precious funds on the little monster, her room suddenly seemed...drab. Sarah looked about, and saw that her bedroom was nolonger the comfortable and pleasant room it had been, as her bed became a lumpy old thing bought from a garage sale and her closet of designer clothes became a mixed mass of cheap, often improperly sized clothes bought by the bag at Goodwill and the Salvation Army. Her carpet vanished, exposing the hardwood floor, and her personal clothes shifted and became a pair of faded pink sweatpants and an ancient t-shirt with a hole in it. She gasped in horror, then saw herself in the mirror...
If she'd been the sort to work hard and make her own money, she'd have had less of a problem. But all the money she'd spent on her personal appearance...had been her parents money, and now...they'd never spent a dime. Her hair was it's natural color (a sort of washed-out brownish blond) with no money being wasted on haircare products, so she had terrible split ends. Her face had never been touched by makeup, and in her washed out simplicity she almost looked pretty in a plain way. A turn-of-the-century country girl. But (braces never bought) her teeth were badly crooked and (bleaching treatments too expensive) vaguely yellowed. She gasped in horror at her surroundings and appearance...then noticed other things.
Her hands were rough and calloused, and dirt was impacted deeply benieth her short, unpainted nails...
("If we're going to be supporting that brat, then she'll work. Sarah can mow the lawn, take out the trash...heck, everything. She'll need to learn an honest trade, 'cause we're sure as heck not going to be paying for any collage.")
...and while her body was tanned and athletic from long hours working in the yeard every weekend, it wasn't the body of someone who did areobics or anything. Her legs and arms were too thick - like someone suited to manual labor - not to mention hairy...because shaving her legs, pits and bush was a waste of time and money.
Through the house, all her cheerleading trophys and beauty pagent ribbons vanished ("You don't have time to waste cheering others on, Sarah. Get a paper route instead...you can start paying us for feeding and clothing you.") and as her cellphone and computer vanished, she screamed at the rock "What did you do? Stop this! I didn't mean to make that wish! Why did I say that anyway?" she walked back and forth in the drab, little room (her bedroom was now on the ground floor, in the little room that had been her mothers office...and her mothers office was now in the larger room upstairs that HAD been hers before the wish...and assumed she'd made the second wish as a...Freudian Slip, or whatever. She closed her eyes and made a wish that would fix everything...