#also have you noticed how Bill loves taunting one twin with the suicide of the other twin

[sage-nebula]

Mabel despises Bill, send post.

Okay, I'll say more than that.

One thing that I haven't seen people talk about (and that I've in fact seen some fan content ignore) is the fact that The Book of Bill makes it explicitly clear that Mabel Pines despises Bill Cipher as of the end of the series. I think there's a tendency to view Mabel as a bastion of love and forgiveness, and while it's true that Mabel does have a lot of love and kindness in her heart, a.) she's not actually an all-forgiving heroine (see: she never comes close to forgiving Gideon for attacking Dipper in "The Hand that Rocks the Mabel"), and b.) we're given explicit text on multiple pages in The Book of Bill that outline just how much she hates Bill and will actually do violence unto him (again) if she ever gets the chance. (Because remember, she got him in the eye with spray paint with extreme prejudice.)

We're first told about this when Bill recounts the story of how he visited Mabel's dreams days before Weirdmageddon in the hopes of making a deal. (Which, side note -- how was that possible? The unicorn hair spell was supposed to prevent that sort of thing from happening. I guess she must have been at a sleepover at Candy's or Grenda's house when this little dream jump occurred.) Bill at first gushes about how much he likes Mabel and would like to sway her to his side, but then:

"Unfortunately, her mind had Wanted posters of me everywhere -- just because I possessed her brother one time!"

Mabel wasn't a fan of Bill's even before "Sock Opera," but as of "Sock Opera" it seems that there's no chance of forgiveness from her for him. And this tracks; in "The Hand that Rocks the Mabel," Gideon treated her horribly. He pressured her into the initial date with him, and then continued to use public pressure and guilt trips in order to keep her locked into successive dates and a suffocating relationship that she couldn't escape from. He was emotionally manipulative, possessive, selfish, and cruel. Despite this, Mabel still felt bad for asking Dipper to break up with him on her behalf and initially went to the factory to apologize to Gideon, until she saw him attacking Dipper through the window. It was only at that point, when he attacked her brother, that Mabel's opinion on Gideon did a 180 and he was no longer worthy of any sympathy or forgiveness in her eyes. Regardless of how he treated her, it was hurting Dipper that Mabel could not forgive.

So it makes sense, then, that possessing Dipper would be the breaking point for Mabel with Bill, particularly considering the note that Bill left for her (and specifically for her, part of it was addressed to her) to find in the car on the way back from the play at the end, as revealed in Journal 3:

"Note to self: Possessing people is hilarious! To think of all the sensations I've been missing out on -- burning, stabbing, drowning. It's like a buffet tray of fun! Once I destroy that journal, I'll enjoy giving this body its grand finale -- by throwing it off the water tower! Best of all, people will just think Pine Tree lost his mind, and his mental form will wander in the mindscape forever. Want to join him, Shooting Star?"

(Yeah, I sure believe Bill that Mabel's a kid he likes. 😬 Maybe "likes" is more appropriate . . . even his lies are lies . . .)

So Bill possessed Dipper on purpose, threw his body down stairs, stabbed forks into his arms, poured soda into his eyes, slammed his hands in drawers, and then had planned to throw his body off a water tower, killing him in what would look like a suicide attempt. I don't think it's any wonder that after this, Bill crossed the point of no return in Mabel's mind. Bill recognizes as such by the time he's finished in her mind as well:

"That was it. She'd never make a deal with me."

It was why he had to possess Blendin in the first place and make up the lie about a way to extend the summer; because thanks to Craz and Xyler, he knew that Mabel was sad about summer ending, and that she could be tricked by someone she thought had a way of extending summer, like a time agent. Bill had to possess a known time agent, because Mabel wouldn't have believed anyone else could do it, and it had to be Blendin because Blendin wore goggles that obscured his eyes (and thanks to fighting against Bipper, Mabel knew how to look for possession eyes, and would never make a deal with Bill). Bill using Blendin to trick Mabel was calculated, and extremely so, because Mabel hates his guts because of what he did (and wanted to do) to her brother.

But it doesn't end there, because then we get to Mabel's letter. (And Dipper's as well, but mostly Mabel's.) Some might be thinking, well, if Mabel knew about Bill's backstory, she might regain some sympathy for him. However, I don't think that's the case . . . because Mabel does learn about Bill's backstory (or at least his history with Ford), and she doesn't feel sympathy for him. Ford's letter not only states that the entire family was reading the book when he exited his lab (and laughing so hard they were crying at it), but Mabel's letter in specific has her write this:

"Anyway, Bill seems to me like a super-needy ex."

We have all laughed and enjoyed this line because of how it further cements Billford as canon toxic old man yaoi, but think about what this means for a moment. This means that:

Mabel has read Bill's backstory, at least re: everything that went down between him and Ford and how heartbroken Bill was over it (she knows about O'Sadleys and the intergalactic Taco Bell incident)

She doesn't feel sympathy, in fact, she's calling him super-needy, which is insulting

Mabel isn't sympathetic toward Bill; she's patronizing. She's one step away from calling him cringe. Her "helpful tips" for how to move on are her condescending to him as she tells him to get the hell away from Ford -- and speaking of which, let's not forget that she says "if you're reading this from space or hell or wherever," indicating exactly where she thinks he very well could be. If she felt sympathetic toward him at all, knowing what she does about his past, I really doubt she'd think he'd be burning in hell.

Mabel ends her letter with this delightful gem.

"Anyway, Bill -- you tried to kill my brother. If I ever see you again, I'm doing this! [illustration of her biting him in half] Deal with it!"

There is no love for Bill Cipher in her heart. There is only a wish to sever him in half, preferably so that his precious eyeball is split in two, with her teeth.

Now, this is in her letter. But we also get some of this in Dipper's letter, too, since she interjects over there. Dipper also delivers a death threat to Bill, and Mabel comments on it. Her commentary praises Dipper's threats (and confident in making his threat):

Dipper: "Come at us again and I'll end you." Mabel: "Wow, Dipper!! So confident!!" Dipper: "Was it . . . was it too confident?" Mabel: "No, it was just right! 13 looks good on you!"

Now, again, this is mostly praising his confidence. But the "it was just right" could also apply to the threat, considering she made a very similar one herself. Many people focus on Dipper's threat to Bill, considering how cutthroat Dipper seemed toward Bill in the show (and how it was their relationship that was focused on because Dipper was the primary protagonist).

But this book has made it explicitly clear that Mabel hates Bill's flat yellow ass with her entire sparkly heart. She wants him away from her grunkle because she knows how badly he treated Ford. And she especially wants to rip him to pieces herself if she ever sees him within a 100 mile radius of her brother again. The idea that Mabel would be forgiving of, or sympathetic to, Bill because of his backstory just doesn't jive with what we know both of her character or her actual, canonical feelings toward him as of the most recent canonical material. Mabel is a loving, kind person, yes -- but she has her limits, and those limits come with those that cause serious harm to her family, just like the rest of the Pines. She's not a two-dimensional, all-forgiving heroine. She's a well-rounded character who forgives when things are forgivable, when it's warranted, when it's deserved. And it's been demonstrated that in Mabel's eyes, certain things -- like trying to cut out her brother's tongue with lamb shears, or possessing him and threatening to throw his body off a water tower -- simply aren't forgivable.