Anything that I can think of would 'hang' over/on/alongside the slide and could likely get caught on clothing or body parts. It's best to train and practice technique to develop the ability to do it without hardware assistance. I'm a female and train females and have excellent results getting other women on track. Generally... only severe arthritis or injury will ultimately prevent someone from being able to rack the slide for loading and clearing, or to lock the slide back.
You have not indicated where your wife is on the slide-racking-continuum, but I'll start at the beginning. Assuming she is right-handed, ask her to:
1) start with an empty, unloaded gun for this exercise, magazine already removed
2) grip the gun as though she is shooting it strong-hand, pointed 'downrange' at all times and with her finger OFF the trigger
3) reach overhand with her left/off/weak hand, and come down on the slide (at the serrations behind the ejection port), getting good purchase on the slide with the heel of her left hand on the left side of the slide, and her four fingers on the right side of the slide
4) NOW, ask her to push forward on the frame with her right hand, while pulling back on the slide with her left - simultaneously. Do NOT baby the slide - push forward hard (right) and fast, while pulling back (left) hard and fast, slingshotting the slide
5) when the slide reaches the end of its travel, let it fly forward - do not ride the slide back
When she understands and performs this flawlessly and repeatedly, move on to practice for locking the slide back
6) with most female's smaller hands, to be able to lock the slide back, they will have to move the gun slightly within their right-hand grip - out of the regular shooting position/grip, and in a right-hander's case, rotating the gun slightly to the left within the right hand. This is necessary to be able to get the shooters right thumb poised under the slide stop in a position to push the slide stop up easily while pulling the slide back/pushing the frame forward as described above. So 3 simultaneous movements - forward on frame with right hand, backwards with slide on left, up with right thumb - with the gun rotated in the right hand slightly to the left of the shooting grip.
7) this must be done safely. Be certain that your wife keeps the muzzle downrange at all times (many right-handers end up pointing the muzzle 180 degrees left). If this is happening, she wil need to turn her body to be certain the muzzle remains downrange.
8) also be careful that she is not 'sweeping' her left forearm with the muzzle while manipulating the slide
Eventually, all this will become easier and happen naturally.
Hope this helps. Welcome aboard.