what does mildred physically look like?

From the text:

'Her face was like a snow-covered island upon which rain might fall, but it left no rain; over which clouds might pass their moving shadows, but she felt no shadow. There was only the singing of the thimble-wasps in her tamped-shut ears, and her eyes all glass, and breath going in and out, softly, faintly, in and out of her nostrils, and her not caring whether it came or went, went or came.'