Siobhan Mailey is a well-off, good-looking girl who initially looks down her nose at Waterloo Road. Siobhan's no pushover, but is impressionable when it comes to the iron will of best friend Amy, and she quickly becomes embroiled in the girl gangs, doing things she'll learn to regret.

Essentially, Siobhan just wants to fit in but when she tries to leave her gang, life gets tough. The girl gang also puts a strain on her relationship with boyfriend Luke – if her mates all think the Waterloo Road pupils are scuzzers, then what must they say about him?