You're right on Celia, but I know Gwenog and Elladora went to Hogwarts the same time together so it's possible they know each other? Elladora was a Gryffindor, but she was really shifty and she didn't interact too much with people beyond a small group. Reading Gwenog's personality, it's possible they could've gotten along pretty well through Hogwarts and maybe kept in touch (especially given her celebrity), if you'd like to say that!