one thing you might want to consider is a little "cheat"... instead of attaching the leg, give her a thigh gun holster or some sort of accessory to cover up the seam.
I really think that would be the best thing to do if you want to stick with Nurbs.
If you do want to convert, you can do so under the Modify menu. Modify > Convert > different options... make sure you mess with the options of the conversion. You can get very different results depending on the conversion settings.