Thankas are the bomb...Get her the high-quality "gold" painted ones instead of any common replica out there.  Also depends which deity you would be choosing.  For me, I'd prefer Milarepa or the Medicine Buddha (where you could also provide a rich story behind their lives).

Below is the link to get these.  However, you'd end up paying half if you had someone ship it over from Nepal instead:

http://www.thangkapaintings.com/