... As part of making the novel a satire, Goldman toys with this veneer of misogyny that isn't nearly as clever or cute as he thinks it is, and part of that is deliberately writing Buttercup as this kind of insipid, vapid, pretty-but-ain't-that-bright kind of person, so when she says, "Everybody always talks about how beautiful I am. I’ve got a mind, Westley. Talk about that," it's kind of comedic, and Westley conveniently says he'll talk about it later so the plot can move along and then never does.
But the movie is not a satire. It's a true story, truer than most things that have ever happened in my life. "I want my father back" is one of those lines that's seared on our collective souls. So the movie has this absence, this lurking shadow where something should be. For the entire plot to happen, Buttercup needs just let Humperdinck carry her off and make her a princess and engage himself to her, and never really minded it or had second thoughts at all until her abduction. She was just ~consumed by emptiness~ and passive. She goes without having a motivation for five years.
And yes, I live with chronic depression, I get that that happens, but then it's like... Do something with it. If she's that consumed by emptiness, how about: She doesn't mind when she's kidnapped. They threaten to kill her and she's like "I mean, I'm dead already, do your worst" If she jumps out of the boat and something in the water might kill her, she's like, Okay sure, might as well. When they get to the top of the Cliffs of Insanity, one of her kidnappers should have to pull her back when she wanders back to the lip of the cliff and looks down it, curiously... and makes riveting eye contact with the man in black climbing up the rope. Make the void do something.
But what if we fill that void?
In the days before she knew she was in love, she tinkled out little tunes on her lute, and could rhyme blue and true as well as the next farmer's daughter. But it was really when her farm boy went off to seek his fortune that her poems became... notable. Sometimes about the intensity of her imagery, the plaintive note in her voice, made people want to listen to her. For all her beauty, sometimes people closed their eyes when they heard her sing about her love, her joy in finding him, her sorrow at his going away, her hope of his swift return.
So when they heard he'd been murdered by pirates, she and her listeners were devastated...
So the Dread Pirate Roberts, on his new ship, heard the news in the form of a quarrel: If a poet is famous for her fidelity to her lost love, and now she's marrying someone else, does that mean she really loved him after all? Did she really?
As I recall, when I was writing my alt version of the story, I put Buttercup's marriage acquiescence as part depression, part the knowledge that as Princess she could do something useful for the country, and part Humperdinck's promise of friendship.