Basic Trope: A character who has been turned non-human and infiltrates the non-humans to help their still-human friends.
Straight: Wendy is bitten and turns into a werewolf. Rather than embrace Transhuman Treachery, she feigns switching sides to help her friends escape the evil werewolves.
Exaggerated: Wendy is very pro-human, and the werewolves fail to notice she's purposely and obviously interfering with their hunt.
Downplayed: Wendy has the flu, and the symptoms are close enough to early stage lycanthropy that she manages to pass herself off as an evil werewolf.
Justified: Wendy is wearing a silver talisman, which interferes with the transformation and allows her a greater degree of independent thought and freedom for evil.
Inverted: Wendy eats some wolfsbane which cures lycanthropy, with the intent to convince the humans that she's actually trying to be good and switch sides... only to disable defenses and let the werewolves in.
Subverted: Wendy convinces her friends to infiltrate the werewolves with her early stage lycanthropy... which was a ruse to get her out of the human camp and tell her new furry BFF's all their defenses and trick them out of their safe haven.
Double Subverted: ...which is actually a double trick meant to lure the werewolves into a trap!
Parodied: Wendy goes all angsty heroine about having to resist the horrible urges for human flesh, and wanting to protect her allies... when she was bitten by a were-rabbit.
Zig Zagged: Wendy flip flops between whom he alliegances are to and who she's really betraying.
Averted: Being bitten by a werewolf isn't enough to trigger "friendly" reactions from established werewolves, all new infectees must first kill a human before being accepted into the pack.
Enforced: The story has Wendy as the heroine, and having her outright do a Face-Heel Turn is just too dark. Hence, Heroic Willpower keeps her good for longer.
Lampshaded: "Hey Wally, you bit that Wendy girl?" "Yeah, why?" "She was snooping on our battle plan and making 'suggestions' to attack an undefended silver mine. I think she's a plant."
Invoked: Wally doesn't like Wendy, and even though she's perfectly evil, he invokes this trope to get the werewolf pack to kill her rather than let her join.
Exploited: The werewolf pack realizes that most converts are likely to try this, so they let them believe it works and have someone follow them to their human friend's hiding place."
Defied: Wally knows Wendy may still have sympathy for her human friends, so he purposely knocks her out with a silver dagger until they're all dead.
Discussed: "How the heck are we supposed to recruit new werewolves if they keep trying to betray us?"
Conversed: "That Wendy girl is taking a big risk, what if the werewolves don't believe her?" "Why wouldn't they? How many people do you think wouldn't jump at the chance to help their friends become like they are?"