I have a 17.5 inch 2003 Trek 7200 (not WSD). I am 5'8" tall, with a 31" inseam, and I think I'm on the correct size. My feet do not touch the ground when I'm on the saddle, but I'm sure it could be adjusted that way if you wanted to. I suspect the bike might be a bit big for her, but the only way to be sure is have her give it a try.