Board Thread:General Discussion/@comment-68.38.73.182-20161126203244/@comment-26397825-20161227054336

Raven was introduced in Volume 2. Yang went on a whole spiel about how Raven is her mother, though I don't think she referred to her by name.

Anyway, long story short, Raven is the woman Yang was talking about in Burning the Candle when she was telling Blake about her mother.