In Order of the Phoenix chapter 4, we meet the portrait of Sirius's mother in Sirius's house. The portrait is behind a curtain and starts screaming. In chapter 6, Sirius tells a few more words about his parents. Neither place seems to mention the first name of the mother, and just call her Mrs. Black.
My question is, what is the canon source that gives the first name? Is it mentioned somewhere in the books? In an interview? On Pottermore? Some other source? Or has someone just made it up and everyone else has copied?