i'm 5'2" and have owned an f2, an 97 gixxer 600, 01, gixxer 600, 03 gixxer 600, and my 05 1k. i've never lowered any of my bikes and i never will. fucks with the handling too much.
i suggest shaving hte seat on whatever you end up getting.
what i would recommend against:
cbr600rr, new r6 (there's no way in hell she's toching on that), aprilia mille's (though those aren't great starters anyways)
i would recommend looking at svs's, 650r's, 03-05 r6 (or the current r6s), etc.
(though unless your chick is auto/bike saavy, even the i4 600's are a bit much to start with)