I think you're approaching this the wrong way.
If she's a terrible shot...she's going to be a terrible shot with whatever is in her hand, be it .22 or .45ACP. I think you should start by finding her a really good instructor. That's what we're here for, you know!
For what it's worth: My wife was a terrible shot too, until this past weekend. I had tried to teach her, prior to becoming an instructor. And other instructors couldn't figure out what was the matter either. Finally, she agreed to let me have one more try. I figured out it was a vision issue. Cross-eye dominance, plus not being physically able to close one eye, nor get the sight picture with both eyes open. Once we put an eye patch over her non-aiming eye, she started shooting GREAT. Obviously not a permanent fix...but a good start, getting her able to see the correct sight picture.