I've done this to three 650's. There are a couple of options including the lowering links as Tim mentions above. However it's best to start at the cheap end and go from there as you may well be able to do the nesessary without having to spend any money.
One of the ladies was 5' 1" with a 29" inside leg.
At the front: you need to slide the stansions (the chromed legs) up through the yokes 1 1/2 inches. But not more.
At the back: (with your lady sitting on the bike with it off the stand and upright) using the ride hight adjust ment, loosen the shock so that she can reach the floor with the balls of her feet.
It's worth mentioning here that MX style boots (the imitations as opposed to the real thing) or a military type boot, will make this easier as their sole extends forward of the toes, more than normal boots allowing the rider to put more of their boot on the floor, thus aiding their confidence.
Once you have lowered the bike enough you will need to adjust the damping in order to re-stabelize the shock. This will keep the handeling correct.
You might need to adjust the bars for reach and slacken off the cluch cable a little for finger length. If you get an 04 or newer bike they come with adjustable leavers.
You also need to make sure the bike is fitted with the standard/lower seat. This is normally fitted to the standard 650, but sometimes is substituted with the higher seat normaly fitted to the GS Dakar.
Using this method most short people are able to ride the bikes with ease.
However if this is still too high you can either fit the Kouba links or alternetively the shorter shock fitted to the low chassis version of the 650 (The low chassis version simply had a shorter rear shock and shorter fork stansions. Otherwise it's the same bike). You will still need to adjust the forks.
I knew a lady of 4' 10" who could reach the ground and turn the bars lock to lock on the low chassis 560gs.
If you need any more help just PM me
HTH Val.