No joke. "Bard whose name I don't know" would make an excellent character title.
Right up alongside Man With No Name from the Dollars Series.
Still if you can't think of a name for her, think up several and use them as different titles. For example. Man With No Name, went by a different name in each of the Dollars movies. He was called Joe in A Fistful of Dollars, because he was an average Joe. He was called Manco, which was Spanish for One Hand. Which was the result of a hand injury he sustained in the previous movie. Then he was called Blondie in the Good The Bad and The Ugly.
In her case, you could probably call her something related to her appearance and instrument. Such as "The Drummer in the Red Shorts." Or some variation of that.