My girlfriend is similar in stature..perhaps slightly taller. After she got her basic strokes down, we demo'd several racquets including the O3 REd and Blue, Head Radicals, TT Warrior OS, Volkl DNX V1, and several others. She ended up hitting the best with the Wilson Surge 5.1 and the TT Warrior OS, but the Warrior was just a hair too heavy for her. So she settled on the Surge.
The Surge is very similar to the Babolat Pure Drive, but has a bit more touch/feel. It was available at the time on the cheap, about 50-60$. It has now been replaced with the NCode Surge, which is not on sale as far as I know, but perhaps you could find a Surge on **** or elsewhere for cheap. It's a good racquet to start out with, b/c it is very easy to generate topspin with, is light and maneuverable, but manageable even for a small weak player, has a generous hitting surface and sweetspot, but small enough that the player is forced to concentrate on tracking the ball, has decent power (hers is strung with a gut hybrid @ 56 lbs.), certainly enough to keep the ball fairly deep even without great footwork, but still retains a high degree of control.
The older 5.1 version is superior to the new NCode version in terms of feel, although I'm sure she will prefer the paintjob of the NCode!
Any of the Pure Drive-esque models would probably do just as good a job too : Pro Kennex Heritage Laver Type S, Volkl Tour-8 V/DNX-8/Cat 8, Prince Shark, etc. (and the vaunted Pure Drive itself of course) The Surge and Pro Kennex are my favorite of the bunch.
Just don't go too lighand stiff or too large-headed....I think it will compromise her development as a player in the long run as it won't encourage proper footwork.
