Can I have some advice on my writing?

I'm trying to write a novel. What do you think of the piece below?



At break I walked into the girls’ toilet and there was Sofiya, standing in the corner smoking a cigarette. She was wearing her nose stud again. I stopped mid-step, shocked.
“Aren’t you supposed to be at detention?” I hissed.
She took a long pull on the cigarette. After she had breathed smoke into the small room she said, “Yes.”
“You do know you’ll be in so much trouble for not turning up?” I asked.
She smirked. “Yes. I don’t care.”
She squashed the cigarette on the windowpane and walked out. I followed her out, completely forgetting about needing to use the bathroom.
“Hey, what’s with this whole rebel-without-a-cause thing?” I asked her, as I walked down the corridor next to her.
“I’m sorry?”
“Do you like to aggravate teachers?” I asked.
“Yes.” She stopped walking and turned to face me. She smiled.
It was a scary smile. Icy cold.
“Perhaps you should know this, Madeline. Or perhaps you shouldn’t. Anyway, I’ll tell you. There’s no alternative, is there?” She frowned. “These pathetic people don’t really have any authority over me. They don’t really know what I can do.”
Her gaze sent shivers up spine. There was something about her…
“Heed my warning, Madeline. I always get what I want and I don’t care if people don’t like it. You’d much rather be on my side than against me.”
“What’s that supposed to mean?”
“You know already.” She walked away.
They were right when they said that foreigners are weird.