The eldest Corduroy child out of five, Wendy (Crossbones) was one of the coolest girls in Gravity Falls, if not the absolute coolest. Her father was absolutely proud of her, and her younger brother, Gideon, adored her for never looking down on him from being different from their family and always being there for him. The two siblings were very close- and then she got involved with Robbie Gleeful.
A while after they started dating, Wendy started to express concerns about her boyfriend and their relationship to Gideon, who encouraged her to break up with him. A few days later, she was found dead. A few days after that, Robbie brought her back to life... sort of.
In the beginning of her life as a zombie, Wendy has no memories of her past life, and she's basically reduced to being Robbie's slave for whatever disgusting desire he wants her to do. (Even though he was attracted to her when she was living, being a zombie makes her even more lovable to him now. Go figure.) It isn't until a certain rich kid accidentally summons a hoard of zombies that she is able to escape her ex-boyfriend.
The summons calls her out to the source, where Wendy sees Gideon for the first time since before her death. Seeing her precious brother triggers bits and pieces of her memories to come back, and she teams up with the kids to send the other zombies back to where they came from. Afterwards, Wendy finds a new home in the high school newsroom, an official Robbie-Free Zone™.