Using a powerful laser would be much neater and cleaner than, say, a buzzsaw. The beam would instantly cauterize the flesh as it splits her body in two, thus there would be no spillage of blood! Also, it is a much more merciful death, as upon contact with the flesh, the intense heat from the laser beam would instantly kill the nerve endings, resulting in no physical pain for the lovely lady. However, the prisoner would suffer mental anguish, I'm sure, as she would live long enough (until the beam reaches her heart) to see her body being vivisected. (Since she is bound to the metal table, a mirror should be placed before her to enable her to watch the drama of her situation as it unfolds....purely out of consideration for her....heheheh.)
Afterwards, she could be made into large "bookends" by covering her two halves with a thin layer, or two, of acrylic resin and then mounting them to some type of decorative fixtures. That would be an interesting exhibit to have at, say, the entrance to a large hallway...truly unique! Yes, you could make a trophy out of your executed heroine....be sure to tell her of your plans for her BEFORE you even turn on the laser, just to heighten her sense of what's in store!
Oh, one suggestion: There should be some small, but secure strap placed across her forehead to hold her head flat to the metal table to ensure that a nice, even divisioning of her is accomplished...right up the middle of her nose and evenly between her eyes.
No pain, no gain. For the villain that is. That is why the laser is computer-controlled to respond to the reflectivity of what it is burning. For now, she feels the approaching warmth between her legs as the steel is cut. When the laser senses it has reached fabric, within nanoseconds it readjusts its power output, dialing it back to split the textile open but cut no deeper. Once that is done, and the woman feels exposed and a slight draft down there, the reflectivity changes for skin and pubic hair signal the computer that the power output should increase to a level similar to that of a magnifying glass focussing its rays from the sun on an anthill. There the beam can linger on her private parts, sweeping up and down an inch or so in eiher direction. For her torture, not her death, there is no need for the laser to proceed any higher.