How does Tennyson show how the emotions of the Lady of Shalott change throughout the ballad?

In the beginning of the ballad, the Lady of Shalott seems contented enough, even though she knows she works under a curse. Since she cannot look out the window to view the world, she has arranged a mirror that reflects the world beyond her tower. "Little other care hath she" implies that she is not distressed by her state; she sings, uses gay colors, and "delights" to work the scenes of the outside world into...

In the beginning of the ballad, the Lady of Shalott seems contented enough, even though she knows she works under a curse. Since she cannot look out the window to view the world, she has arranged a mirror that reflects the world beyond her tower. "Little other care hath she" implies that she is not distressed by her state; she sings, uses gay colors, and "delights" to work the scenes of the outside world into her weaving, showing that she even has a degree of happiness and satisfaction with her lot. 

However, when "two young lovers lately wed" are reflected in her mirror, a deep dissatisfaction rises in her, and she voices it, saying, "I'm half sick of shadows." "Half sick" is certainly an understatement, suggesting she has become angry and desperate. The vision and voice of Sir Lancelot provide the motivation for her to risk everything for a chance at life. We're not told what she feels or thinks when "she left her web, she left her loom," but her determined "three paces through the room" indicate that she has resolved to rebel against her fate. 

She floats down to Camelot with a "glassy" expression, like a "seer in a trance." This indicates she is resigned to her death. She does not wail or act out because of her coming doom, suggesting that she may feel she has made a worthwhile exchange. Though she doesn't want to die, certainly, she seems to be at peace, for she resumes her song until "singing in her song she died." The song was "mournful, holy," showing that she was sad to leave this world, but no bitterness, anger, or thoughts of revenge tainted the beauty of her melody. The fact that Lancelot deemed her face to be "lovely" implies again that her end was peaceful and that she did not regret her decision to pursue freedom, even though it cost her everything.