I have her, stil awaiting assembly. Her cloak/skirt is incredibly long, and is lifted by a familiar. If you remodelled her, cut the cloak at an appropriate length, she could probably be mounted like the old Morgan Le Fay model. But you will have to do some cutting, the cloak is easily twice her length...
Oh, and the throne doesn't attach to her back, so you don't need to worry about that, unless you were planning on using the whole saddle.