Billie

Belinda is a major character. She was a recurring character from Season 3, up until Season 5, and made a guest appearance in Season 6. Billie is Ryan's blood twin sister, and is the first female LGBT character on the show.

Biography
Billie was introduced in the Season 3 Premiere as the "wild child" known as Ryan's sister. She was immediately jealous of Ryan's connection with Emelia, and seemed to like nothing more than causing trouble within the school. As a headstrong character, she often butted heads with other characters, disagreeing with their choices, and wasn't afraid to speak her mind. During her time on the show, Billie received a number of important storylines, such as drug addition, bulimia, and dealing with her sexuality as a lesbian.

Season 2
Bille was first mentioned in the Season 2 Finale where Ryan asked her dad "Where's Billie?", although she didn't make an appearance until Season 3.

Season 3
Billie was introduced in the Season 3 Premiere as Ryan's sister. She was immediately jealous of Ryan's connection with Emelia, and seemed to like nothing more than causing trouble within the school. She quickly butted heads with Rachel as she also wanted to be seen as a female lead, and demanded the lead solo in an upcoming performance, but Damien decided to give it to the more experienced Rachel. Billie was not happy with this decision, and decided to challenge Damien, where he conceited and allowed Billie and Rachel to "audition" for the part. She wanted to be close with Ryan and was threatened by anyone who was close to him. She started to manipulate Ryan in order to push others away. As others managed to catch onto what Billie was doing, her actions lead to her having a falling out with her brother, leaving her feeling isolated and alone, and turned to dieting in order to feel control in her life, as well as starting an aerobics group that allowed her to feel powerful and in control. She broke into the hospital using Hannah's pass to steal what she thought were diet pills, but heard someone coming and grabbed the first thing she could find. After the pills didn't work, she resorted to making herself throw up. In the Season 3 Finale, she contemplated taking her life, but was stopped when a mysterious boy interrupted her. She made peace with everyone she had hurt, and joined the group for their performance during the Football Grand Final, where she was a victim of the explosion.

Season 4
Billie is revealed to have survived the explosion, and finds out the boy who "saved" her is named Xavier, and is interested in joining the club. Xavier joins, and the two form an unlikely friendship, although the two struggle as they are complete polar opposites, and Billie's attitude tends to be hard on Xavier. Shannon quickly caught onto Billie's bulimia and threatened to expose her secret. Although she never threatened Billie, she felt pressured into doing exactly what Emelia said in order to protect her secret. Shannon quickly became too much for Billie to handle, which lead to her exposing her secret herself. After Ryan went blind, Billie tried her best to be by her brothers side, but struggled adapting to his new life as she blamed herself. In a moment of weakness, she found out that Ryan and Emelia both had feeling for each other, and alerted the whole club, leading the two to feel embarrassed. Billie was upset with what she had done, and tried to ask for forgiveness, but everyone, par Xavier, felt she was out of chances. Billie decided to man up and apologise, something she wasn't used to, and she received forgiveness, though everyone questioned how long her new attitude would last.

Season 5
Much to everyone surprize, Billie had managed to keep her good girl attitude going for a decent amount of time, and she meets a girl named Charlotte. At first sight, Billie wants to be bestfriends with Charlotte, but can't understand why. After helping Xavier accept his sexuality, Billie feels that she may have feelings for Charlotte, but is afraid to admit them. After a long game of cat-and-mouse, Billie finally confesses her feelings to Charlotte, and accepts her sexuality. The two begin dating shortly after. After Jake graduates, Billie stops attending Glee Club meeting, as she doesn't feel it's cool anymore without Jake. Eventually she drops out all together and focuses all her spare time on her aerobics group.

Time Jump
Billie went to university and received a degree in Health and Fitness, creating her own official aerobics group. She also managed to start her own morning TV fitness. show

Season 6
Billie returns with Charlotte - still dating - in order to show her support to Jake. After he dies, Billie tries to lift the spirits of everyone else, though her efforts fall flat.

Trivia

 * Billie was never meant to receive as much attention as she did. She was only meant to appear as a minor character to "shake things up". After her introduction, the writers became heavily interested in her character, and decided to feature her in more storylines.
 * Billie was never written as a lesbian character, and this was later added once the writers felt that discovering her sexuality was important to her journey.
 * Billie seems to be partly inspired by singer Avril Lavigne.