About her singing in her words:

I believe that the natural sound of my voice best matches with Wagner, Russian music, perhaps also Brahms.
There are some Brahms' songs of high tessitura, Mahler's songs, pieces of Bach or Lutoslawski in which I need some form of piano. Such effect requires special measures, using a special resonance of the head.

It is quite complicated, but the overall problem comes down to control of the emotions. Someone could accuse me of keeping everything under exacting control, checking, experimenting and therefore my singing seems cold. Perhaps this is true, but I prefer controlled singing to hysterical emotions which ruin the technique. Many opera singers cannot manage songs or oratorios. This is only just because of such lack of skill. You cannot transfer overburst, huge emotions, digestible in Werystic opera, to Bach's intricate arias, Mozart's and many songs of all eras.

I am trying to pass this on to my students, who often when working on their technique forget about the expression and vice versa.

Singing has to be a skillful delivery of feelings, emotions, and the bottom line is to love the music and desire to endow others with the beauty of art.