Buttercup is a farm girl who lives in the country of Florin and is the true love of Westley. When he works on her family's farm, Buttercup refers to him only as "Farmboy" and loves to order him around. Westley would not argue with her but would only obey her commands and reply "As you wish." Over time, she realizes that when Westley says "As you wish" he is really saying "I love you." In time, she realizes that she loves him just as strongly, too.
When Westley goes away to find his fortune, his ship is attacked by the Dread Pirate Roberts, and the story gets back to Buttercup that her love has been killed by the pirate who never takes prisoners. Devastated to learn this, Buttercup shuts herself away in her room, forgoing sleep and food. In the end, she decides that, while she may live on, she will never love again.
Five years later, Buttercup forced to become betrothed to Prince Humperdinck. Although she does not love him and tells the prince so, Humperdinck pushes forward with the wedding, assuring her that, with time, she will come to love him.
While she does not like the idea of marrying her prince, she does still enjoy riding her horse. While out one day, she comes across three men claiming to be lost circus performers and, before she can do anything, is knocked unconscious. When she awakes, she realizes she's now on a boat in the middle of the sea, kidnapped by the men, who she learns are names Vizzini, Inigo, and Fezzik. Vizzini, the band's leader, announces his plans to start a war with the neighboring country of Guilder by killing the princess and leaving her body on Guilder soil. The other two men don't seem keen on following this plan and an argument breaks out. Buttercup uses this opportunity
Buttercup plans on committing suicide rather than be married to Humperdink, to which the Prince replies 'Please consider marrying ME as an alternative to suicide' to which Buttercup agrees, but still plans on killing herself on their wedding night and she is about ready to go through with it, plunging a dagger into her heart, when she and Westley are re-united and defeated Humperdink, then go off to live their lives happily ever after.