Rhiannon is the main antagonist in the novel Candyfloss. She is a very rich and beautiful girl who used to be Floss' best friend.
Rhiannon is the most beautiful and popular girl in Floss' class and everyone wants to be her friend. Much to Floss' happiness, Rhiannon befriends only her, but their friendship isn't as good as it should be. Rhiannon is very bossy and often rushes her friend around, never forgetting to mention how many expensive present she gave her.
However, after one year Rhiannon gets bored of Floss and decides to befriend two arrogant girls, Margot and Judy instead. She still claims to be Floss' best friend and even gives her a really pricey bracelet for her birthday, but she also doesn't care at all when Margot takes it away from Floss.
Rhiannon also taunts another girl, Susan, who is new and very smart. She despises the nerd, kicks her during lesson and even makes fun of her poem. When Susan throws the bully down in order to protect herself, Rhiannon makes a scene, claiming Susan broke some of her bones.
Since Floss starts living with her father who owns a local café, it is sure her friendship with Rhiannon is almost over. Her friend only pooh-poohs when she sees the dirty café. Floss starts coming to school in dirty clothes which smell like fat. Margot and Jude makes fun of that and call Floss names and Rhiannon joins them. She later claims to angry Floss it was just a fun, but the girl doesn't believe her at all.
Meanwhile, Rhiannon's mother thinks Floss is a very deprived and poor kid, and forces Rhiannon to invite Floss. The three go shopping and Rhiannon's mother buys Floss very expensive clothes, making the girl feel very unpleasant.
Next day at school, Floss hears Rhiannon talking to Margot and Judy about the shopping. She defames Floss so much she runs to Rhiannon and breaks their friendship for once and all. Since then, Floss befriends Susan and Rhiannon starts bullying them both, defaming Floos in front of students, insulting her father for his obesity, destroying her things and writing abusive poem in the restroom.
To avoid bullying, Floss wants to change seat and sit next to Susan at school, but the teacher doesn't allow it... but only at first blush. Rhiannon soon provokes Floss so much she hits her with a ruler, causing Rhiannon to make a loud scene. To "punish" Floss, the teacher tells her to sit next to Susan.
Since then, Rhiannon spends time only with Margot and Jude and they defame Floss and Susan every time they can. Floss has soon enough of being taunted and kicks the bullies' butts during PE. As a revenge, Rhiannon reveals Floss that her mother plans to call a social worker on Floss and her father. It actually doesn't happen, but scares Floss to death, as she loves her father. Later, angry Floss tells the bullies to leave her and Susan alone. She also says Rhiannon's doesn't have to worry, as Floss and her father are going to start a new, better life. The three bullies, surprised by such a defense from their victim, quickly leave.