ok, good for her for wanting to move up!
ok, take it from a shortie..

best bet is a F4i... why? the saddle isn't WIDE like the Kawi 636. Secondly, I've lowered plenty of bikes in my time and I can tell ya, if you do it correctly, there is NO handling problems. I don't know how your going to go about "lowering" it, but here's what I've used in the past...
http://www.ohlins.com/index.htm or
http://www.foxracingshox.com/website/homepage.asp now YES they can be spendy, BUT they work GREAT!
Hope that helps.............
japbike
p.s. How long has she been riding?! How tall is she?