In the story, the princess knows that, if she leads her lover to the door with the tiger, her lover will be torn to pieces. Yet, despite this terrifying prospect, the princess wonders whether it wouldn't actually be "better for him to die at once, and go to wait for her in the blessed regions of semi-barbaric futurity." She imagines that if she cannot marry him on earth, death will eventually join them in wedded bliss.
The princess is also motivated to deny her lover the prospect of marriage to the beautiful courtier. The text tells us that with "all the intensity of the savage blood transmitted to her through long lines of wholly barbaric ancestors, she hated the woman who blushed and trembled behind that silent door." After all, this beautiful courtier had dared to "raise her eyes to the loved one of the princess." So, the princess' violent jealousy may motivate her to lead her lover to the door with the tiger.
Alternatively, the princess may be inspired to simply spare her lover the prospect of a terrifying and gruesome death. If this motivation holds sway, the princess will likely lead her lover to choose the door with the maiden. However, many think that, with the princess' jealous nature, the prospect of her sparing her lover a violent death is in doubt, despite her love for him.