Coriander Bloom comes from a tight knit wizard family. All of her relatives live in the same city she does, and so her parents never thought she would need muggle friends. This caused her to grow up somewhat isolated, until she started breaking rules just to meet her social needs. This escalated into thrill seeking, and now Coriander is what most people would consider a 'bad kid.'
Coriander isn't exactly the smartest, but she tries hard enough to keep others off her back. Most of the time, at least. She understands enough to be grateful that she was born a witch instead of a muggle. Growing up, she was homeschooled, but learned how to study and write essays and everything she would ever need to know at Hogwarts. Her favorite subject is Potions, due to the focus that goes into it.
Coriander will do just about anything if there's a dare or bet involved. She's not afraid of much, failure being her worst fear. Because of this, she does some pretty stupid things. Reckless would probably be the word to describe it. Despite this, deep down she has good intentions. She'd never hurt anybody unless they hurt her first, although the same can't be said for annoying people. She might be very, very hard to handle, but she's a good kid.