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. Gwen, on the other hand, dislikes Sierra because of her stalker-like tendencies as well as her disgusting habits. When Sierra and the rest of Team Amazon found out that Gwen kissed Duncan, Sierra allies with Courtney only so she can finally get rid of Gwen once and for all so that Cody would then focus on her instead of Gwen. After Gwen's elimination in Picnic at Hanging Dork, Sierra becomes delighted, but then realizes that Cody misses Gwen, much to her own dismay.

Their conflict has subsided by Total Drama All-Stars as Cody isn't a contestant while the two of them are. Although Sierra didn't display any hostility towards Gwen like last time, Gwen still dislike Sierra especially after she shows the same affection she had for Cody to Cameron, whom Sierra begin to see as Cody. It is also revealed that Sierra is an epic supporter for her relationship with Duncan, even making several blogs about them.

Celebrity Manhunt's Total Drama Action Reunion Special
Gwen is disturbed when Sierra reveals that she knows personal information about the cast.

Super Happy Crazy Fun Time Japan
Gwen is grossed out after watching Sierra sniff Cody's shoe and seeing its lace go up her nose and out through her mouth. After winning the challenge, Sierra calls for a group hug, but, while hugging Cody tightly, angrily tells Courtney, Gwen, and Heather to "back off" as soon as they begin coming closer.

Anything Yukon Do, I Can Do Better
When Cody attempts to cuddle Gwen for warmth (much to her displeasure), Gwen simply pushes him to Sierra, whom happily hugs Cody.

The Am-AH-Zon Race
Gwen is disturbed when she finds out that Sierra is using a pizza box as a laptop and an actual mouse as a computer mouse. She quickly rejects Sierra's offer to use it after she is finished with it. When Chris asks one of the members on Team Amazon to carry Cody's EpiPen, Cody begs Gwen to take it instead of Sierra, who reluctantly agrees to do so, much to Sierra's dismay. Sierra complained about this arrangement, claiming that she knew more about Cody's life threatening allergies than anyone else on the team. When they are caught by the Zing-Zings, Heather orders Gwen to reach into Cody's pockets for the lantern's batteries. Sierra then 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 the challenge. Despite being jealous of Gwen's hold over Cody, as well as angry at her for cursing the team with her good luck prediction, Sierra agrees to vote Heather off with Courtney and Gwen.

Can't Help Falling in Louvre
After hearing Sierra cry throughout the first challenge, Gwen furiously yells that she cannot take it anymore, and leaves her behind with Cody, as she, Courtney, and Heather exit, telling him that he needs to deal with her.

Greece's Pieces
Prior to discovering the kiss, Sierra approves of the concept of a "Gwuncan" relationship. Later, when Courtney finds out about Duncan's betrayal, Sierra restrains her from attacking Gwen, expressing a worried look on her face, despite siding with Courtney by ordering Cody to lose the challenge, so that the team can eliminate Gwen from the competition.

The EX-Files
In this episode, Sierra is shown to have developed a strong hatred towards Gwen. She angrily 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. When a lizard climbs up Heather's leg and forces everyone to run into 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 comment about how obvious Gwen and Duncan's attraction was. At the base, none of the teammates are 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
In the first class section, Sierra and Courtney glare ominously at Gwen. Sierra does not interact with Cody for a while because she is too focused on her hatred for Gwen. Sierra joins Courtney's alliance to vote Gwen off if they lose. 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, strengthening their dislike for each other.

Sweden Sour
Sierra is delighted that Gwen is gone and refers to Gwen as her an enemy in a confessional. She claims that Gwen's absence will lead Cody to realize who his true love is, while pointing at herself. Sierra is also mad when Cody constructs a huge wooden replica of Gwen's face. She says Gwen's head is empty and thought of the idea of cutting the replica of Gwen's face and used it as a boat, in which both Heather and Courtney agree.

Niagara Brawls
When it is first thought that Gwen will be returning, Sierra, along with Courtney and Heather, looks disappointed.

Awwwwww, Drumheller
When Cody's sleep-talking indicated 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.

Heroes vs. Villains
Sierra tells Gwen that while many fans seems to be upset about her being in a relationship with Duncan, Sierra shows support, saying that she understands and also state that their relationship is similar to hers and Cody. Gwen then sarcastically thank Sierra for being supportive.

Saving Private Leechball
After Sierra accidentally flings her leech at herself while trying to aim at Gwen, she daydreams about Cody. In the confessional, Gwen gags at that remark as a result.

Suckers Punched
When the Villainous Vultures are given the chance to vote off one of the Heroic Hamsters, Gwen speaks for her team and says they choose to eliminate Sierra. She also seems to feel sorry for her. Before Sierra takes the Flush of Shame, Gwen also asks Sierra to say "hi" to Cody for her.

Trivia

 * In both seasons they competed in one of them finishes in fourth place while the other finishes ninth.
 * In the season which they came fourth they appeared in every episode of the season (despite not being a finalist).
 * Both were involved in a love triangle with the Cody, arguably also with Cameron depending on whether Cameron and Gwen are considered a couple.
 * Both were targeted for elimination by someone else’s elimination campaign, where the other competitor agreed aid in
 * Courtney wanted to get rid of Gwen, which Sierra supported.
 * Cameron wanted to get rid of Sierra due to her stalker-like tendencies, which Gwen later helps him accomplish.