Yup that is Rin! From Fate Hollow Ataraxia to be precise. The stick she has is a magical artifact that can grant her the abilities that she could possess in other parallel worlds(or something along those lines). As such she can 'borrow' the power of a fully adult version of herself. The catch is the Stick doesn't like its creator or user, so guess what! Great power at just the cost of your dignity! What a trade!
http://img73.imageshack.us/img73/1691/hollow2331cv.jpg Is that Rin? It looks kind of wrong for someone like her
