Who was queen of the witches?

Her name was Hecate. She is referred to in Hamlet, A Midsummer Night's Dream, King Lear, and Henry VI Part 1 as well as in Macbeth. Her addition as a character in Macbeth is widely believed to have been the work of Thomas Middleton, since all of the scenes with Hecate are not in Shakespeare's style, and employ songs known to have been used in Middleton's play The Witch. One imagines that Middleton was asked to tart up Shakespeare's play with some snappy song-and-dance numbers.