Rue is... a complicated character. I didn't think much of her at first. She was an okay character, but it was mostly Mytho's character that made her odd. His lack of emotion and all that. Made me wonder if he really wanted to be her boyfriend.
And then: Plot Twist!
When she revealed herself to be Princess Kraehe, the dark magical girl, and she started acting very jerkish, really goading Tutu to reveal her love for Mytho, which would of course make her disappear.
Of course there's more to Rue than a possessive jerk. Character development kicks in in the second half and suddenly she's among the most lovable characters. She is a bit possessive, not wanting Mytho to regain his heart for fear of him realizing he doesn't love her. But with her sucky life one can understand her feelings.
I almost skipped the Femio episode, but I'm glad I didn't because it brought up one of the most powerful moments in the series. Repeatedly throughout the series her "father" tells her that no one except the Mytho will love her, so when she tries her hand at acquiring a sacrifice for the raven, this comically exaggerated character by the name of Femio is able to resist her charms... which the raven uses as the ultimate proof that his "daughter" is ugly and unlovable. Jerk.
Like many, many characters Rue is hated by a portion of the fandom that feels that Ahiru and Mytho should be together. I disagree with that, as I the Ahiru x Mytho ship seemed to be purely physical, to the point that even Ahiru herself questions her love for him. Rue's bond with Mytho on the other hand is much more meaningful, and Ahiru x Fakir is okay too.
And now one last thought.
HNNNNNNNNNNNNGGGG~
Subject: Character Discussion - Rue (Princess Tutu) 
