Mistborn

There once was a girl who lived in a small town. She was sad because she didn't have any friends. Her mother told her that she had to come home directly after school and she wasn't allowed to play with the other kids. Then one day she said “tomorrow you can play with the other kids as long as you are careful.”

The next day the girl started playing with the other kids. They rode on their bikes and had fun, but the girl still didn't feel like she belonged. The others told her that if she wanted to truly belong to the group she had to help them with something.

In that town most of the people were poor, but there was one boy who was rich. His father was a doctor or something and he always had much better toys and clothes than the other kids. Because of that everyone hated him and the kids liked playing tricks on him. Now they'd figured out a new way to mess with him. They stole a wallet, some jewelery or something similar and blamed it on the boy. The only problem was that no one would believe that the boy had really done it. That's why they needed the girl's help. The adults would believe whatever she said.

So in the end she stood in front of the policeman and had to choose whose side she was really on. On the one hand the boy was probably really nice once you got to know him, but if she didn't lie she'd be alone again, so she did as the kids had asked.