She looks... sad. Like what I would imagine her being Lady Kuchiki as.
Trapped in a golden cage, and the bars, duty. Fulfilling her role with grace, but that was never what she wanted. The gate behind her adds to the whole 'caged' impression. And there's this... melancholy curve to her mouth, and she's looking down, and... just. It's heartbreaking.
Just my impression. It's beautiful, elegant, lovely. Just... overwhelmingly sad.