SOLVED. New girl in school/ is boycotted by her friends/ enters an alternate dimension in to the future/ She and her brother are evil rulers [s]

[Roopkatha]

The girl goes with her mom to the grocery store and there is a mishap in the parking lot(there's snow and its slippery), and her only friend who was supporting her has an accident and somehow she believes that the girl pushed her in harm's way.
So now she all alone and hates the world. Then she travels to this alternate dimension in the future where the town is ruled by an evil ruler. There are these guards with lasers who shoot to kill the people who are out in the streets after the imposed curfew.
She struggles to get back home and meanwhile lives at the house of a kind family who give her refuge. In the end, she comes to know that the ruler is her future hateful and ugly self and her brother, who just wants to see her avenged.
When she finally gets back to her world, she realizes that this was how the future would turn out if she gave of on the world and turned hateful.
But ironically, the ending was a bit different. As in she travels to a wrong dimension? Guys, I am not sure but please help me and this has been driving me crazy!!
Any ideas??
(read this book in the year 2014)

[Valerie]

At the beginning of your description, I thought this was Trial by Fire but now I'm not so sure.

[Roopkatha]

Yes that book's description does seem to match mine roughly, but I'm afraid that's not the one :(

[Avaminn]

Sounds vaguely similar to So You Want to Be a Wizard but that's a bit of a stretch...except I never finished that book so maybe that's right?

[Justanotherbiblophile]

Nope, it's not SYWtbaW.
Nita doesn't go to a parking lot w/mom, a bully already hates on her. She's not all alone, gets a male friend. They got to evil dimension, they don't meet themselves.

The scene with the car is gripping. I've started writing it up for the 'best scenes in novels' over in chat.

[Roopkatha]

Guys thank you so much for your help but I found the book!! I just remembered why she had had the fall out with her "friends". They had challenhed her to steal an important school trophy if she wanted to be in the in-crowd.
So I googled "steal school trophy book" and got Thief! ^_^