How does her voice not fit an empress?
And if you think it doesn't, why is that bad? She was a commoner, after all.
Also I think they did an excellent job with her voice and animation mannerisms. Reminds me of my relatives in Taiwan.
I expected her to somehow sound older, right now she's like a young adult. Maybe it was just not my cup of tea.
Ah, I did not know that she was a commoner. If I had to judge the formality in her lines I would say it's medium - more formal than you'd talk to a friend but less than greeting a leader. For example when she says "you", I'd expect her to use the formal "您" (nin) and not the less formal "你" (ni).
Her animations are rather nice and the music is gorgeous, it's just her voice that irks me a bit.