Gwen and Sierra

This article focuses on the interactions between Gwen and Sierra.

Overview
The conflict between Gwen and Sierra is mostly one-sided on Sierra's side, due to her intense jealousy of Cody's feelings for Gwen, as well as her disgust about Gwen's actions during Total Drama World Tour. It reached a high point after the events of Greece's Pieces, when Tyler revealed that Gwen and Duncan kissed, This revelation intensified Sierra's hate for Gwen, and ultimately ended in Sierra helping Courtney to vote Gwen off two episodes later.

Super Happy Crazy Fun Time Japan
Gwen, along with Heather and Courtney, are grossed out after watching Sierra sniffing Cody's shoe and seeing it come out of her mouth. After winning the challenge, Sierra calls for a group hug, but then tells Gwen, Courtney, and Heather to "back off" once they start to come closer to her and Cody.

The Am-AH-Zon Race
Gwen is disturbed by Sierra when she finds out she is using a pizza box as a laptop and using an actual mouse as a computer mouse. She quickly rejects Sierra's offer to use it after her. When Chris asks for a team member to carry Cody's epipen, Cody begs Gwen to take it instead of Sierra, which she has to agree to, much to Sierra's dismay, claiming she knows more about Cody's life threatening allergies than anyone. When they are caught by the Zing-Zings, Heather orders Gwen to reach into Cody's pockets for the lantern's batteries. Sierra complains about not being the one reaching into Cody's pockets. Later, Sierra is annoyed by Gwen's snoring, claiming that she was driving her crazy. After their team lost the challenge, Sierra and Courtney glare at Gwen when she wakes up and asks if they had won. Like Heather, Sierra thinks Gwen is responsible for jinxing their team. She then agrees to vote Heather off for their loss, if Gwen promises to stop being nice to Cody.

Can't Help Falling in Louvre
After hearing Sierra cry throughout the first challenge, Gwen furiously yells that she couldn't take it anymore, and leaves her behind with Cody.

Greece's Pieces
After learning about Duncan and Gwen's kiss, Sierra sides with Courtney by ordering Cody to lose the challenge, so that the team could vote Gwen off.

The EX-Files
In this episode, Sierra is shown to have developed a strong hatred towards Gwen, along with Courtney. She makes a paper cut-out of Gwen and then bites its head off, while singing an altered version of the nursery rhyme Rock-a-bye Baby. Later, in the confessionals, although she says that she saw Duncan and Gwen's attraction coming since season one, she still believes that stealing other girls' boyfriends is wrong. She even seems as furious at Gwen as Courtney. When a lizard climbs up Heather's leg and everyone ends up in the middle of the minefield, Sierra immediately blames Gwen for leading them to the trap, labeling her as the "New Heather." Though she doesn't sing in Boyfriend Kisser, she does make a line about how obvious Gwen and Duncan's attraction was. At the base, none of the teammates is able to find an artifact, until Gwen finds the alien cube. Sierra and Courtney are the only ones upset at her, seeing as how she won the challenge and made herself safe.

Picnic at Hanging Dork
At the first class section, Sierra and Courtney keep glaring ominously at Gwen. Sierra even does not bother Cody for a while. Sierra joins Courtney's alliance to vote Gwen off. Additionally, Gwen tried to be in an alliance with Cody, telling Cody she would help get Sierra voted off after Courtney if he joined forces with her.

Sweden Sour
Sierra states this day is the best, as Gwen is gone. She appears in the confessional saying that she's happy about Gwen's elimination, even saying that she was her foe, and that Cody can finally remember who his true love is, while pointing at herself. Sierra is also mad that he constructed a huge wooden replica of Gwen's face in We Built Gwen's Face.

Awwwwww, Drumheller
When Cody started talking in his sleep and revealing that he was having a dream about him and Gwen, Sierra quickly woke him up. When he asked what happened, she told him that he was having a nightmare.

The Am-AH-Zon Race
Despite being jealous and being mad at Gwen for cursing the team with her good luck prediction, Sierra agrees to vote Heather off instead of her, on the condition that she wouldn't "be so nice to Cody."

Greece's Pieces
Prior to discovering the kiss, Sierra does in fact acknowledge and appears to approve of the "Gwuncan" relationship. Later, when Courtney found out about the kiss, Sierra physically restrained her from attacking Gwen, and had quite a concerned look on her face.