"My people are dying, Sokka. Those who are in charge of others have a responsibility. It is time we show the Fire Nation we believe in our beliefs as much as they believe in theirs."
— Yue to Sokka in The Last Airbender.
Princess Yue was the sixteen-year-old ruler of the Northern Water Tribe at the North Pole. Her character is a composite of her animated counterpart and her father, functioning as both Sokka's love interest and the head of state due to her father's untimely death.
Princess Yue told Sokka that she was a stillborn baby until she was revived by the Moon Spirit:
"My hair is white because when I was born, I was not awake. My mother and father could not get me to make a sound or move. They prayed for days to the Moon Spirit, then they dipped me in the sacred waters. My parents said that my hair turned white then, and life poured into me ..."
The siege of the north
When Aang and the others arrived at the Northern Water Tribe, she welcomed them and befriended Sokka, who became her love interest. When the Fire Nation fleet came to invade the Northern Water Tribe sixteen years later, Commander Zhao captured and stabbed the Moon Spirit to death. This caused the moon to turn red and Yue to faint and weaken.
Yue gave her life back to the Moon Spirit by lying beside it in the oasis pool. Blue-white life-force energy leaped from Yue onto the Moon Spirit. In the process, Yue's hair turned from white to black. Unlike the animated series, Yue's body did not disappear or transform into the new Moon Spirit. The Moon Spirit swam again and rejoined its partner, the Ocean Spirit. Iroh subsequently lifted her lifeless body out of the pool and put her on the ground, and Sokka grieved over her death.
Yue was a kind, gentle, faithful and hopeful person. She was extremely protective of her people, and was determined to do anything to save them, going so far as to giving up her own life to resurrect the Moon Spirit.
Yue found her love in Sokka, a seventeen-year-old warrior from the Southern Water Tribe. However, the relationship came to a tragic end when Yue sacrificed herself by giving her life back to the Moon Spirit. Her death had greatly affected Sokka.
Yue (月) means "moon" in Mandarin Chinese. In Japanese, it is pronounced as "yu-eh", as heard in the series and the movie. The name also means "tragic accident" in Japanese (夕映) and is traditionally given to Japanese children who die shortly after birth.
In the series, Yue was the only member of the Northern Water Tribe wearing purple while others wore blue, which highlighted her character from the rest. In the film, Yue wore blue like her people, but she was the only one with darker skin tone, as others were mostly cast with white actors.
As opposed to the events in the series, Yue's father, Arnook, was already deceased in the movie, and thus Yue was the ruler of the Northern Water Tribe.
The entire subplot regarding Yue's engagement with Hahn was cut in the movie, meaning the romance between Yue and Sokka went on without the "other man" in the relationship.
Unlike the series, Yue's lifeless body remained even after becoming the new Moon Spirit. In a deleted scene of the movie, Yue's death affected Sokka greatly, even to the extent of asking Aang to save the city for Yue.
To make up for the lack of romance between Sokka and Yue in the original cut, M. Night Shyamalan extended the scene right before Yue gives her life to the Moon Spirit, which includes the line, "It is time we show the Fire Nation we believe in our beliefs as much as they believe in theirs," alluding to the Fire Nation way of life where people could not agree to disagree on something as personal as one's own belief.
Yue's "believe in our beliefs" line is often criticized for poor or redundant wording, even though "believe in belief" is a common topic for theological discussions.