Mabel's Deal

Mabel and Dipper permanently live in Gravity Falls after a nameless issue with their parents, and are now graduating from high school. After getting invited to a big party for the graduating class, Mabel finds out her brother won't be attending and plans to just stay home like always. She decides to take matters into her own hands and make a deal that would free their enemy but get her brother a friend other than just herself. Maybe it'll work, maybe Dipper will find out and hate her, or maybe there will be a loophole that no one saw coming.