Sierra

Sierra is a teenage girl from the Transformers: Prime franchise! She shares the same homeroom as Jack Darby and is the captain of the high school's cheerleading squad!

Prime Cartoon
As Jack was pretending to ride a motorcycle and talking to it about how he would like to own it, Sierra and Evette caught him in the act and mocked him for talking to what she thought was his motorcycle. Flustered, Jack to explain his away his embarrassment while also flirting with her. When two purple cars, seeking out the motorcycle, appeared and threatened to run them over, Sierra and Evette fled.

Another day after school, she tried to take Jack up on his offer for a bike ride. They were interrupted by Vince, who challenged Jack to a street race. Sierra and Evette accompanied them to a road outside town where they held the race, and Jack easily won! Sierra and Evette spread news of his victory around the entire school! She later told Jack she was impressed with his racing skills. Jack subsequently felt compelled to accept Vince's second racing challenge: Take part in an illegal street race. Sierra acted as the starter and waved to Jack before the cars blasted off. The next day, she again asked Jack if he'd give her a ride. At first he turned her down, but changed his mind a short time later!

She was talking with Evette outside when Raf was picked up by an ambulance belonging to a friend of Jack's mother.

In the wake of the Omega Lock attack, Agent Fowler had the whole town of Jasper evacuated. This most likely included her and Evette.

Ratchet & Clank: Twinsanity
A few days after the Omega Lock attack, Sierra saw a video-game character named Turbo (with his King Candy persona still intact) destroy all of Jasper, Nevada! She had to find Evette so they could escape the destruction that Turbo has caused. They were both forced to leave their home town in search of somewhere where they can live peacefully! They ended up on Twinsanity Island, which is located only in the mysterious 10th Dimension!