As an owner of a Pinnacle Grace quilting frame and a Bably Lock Pro Quilter machine, I want to say: Don't do it!
The writer that told you that a frame with a home sewing machine is a waste of resources, is exactly correct.
If you are duty bound to spend $$ ... to help your wife quilt her quilts, along with having her help you, the other suggestion I would make is a workcenter that has a big enough space to quilt a quilt on her table machine without having to fight keeping her quilt under her needle. A cabinet that allows her to have her sewing machine level with the work area would be a big help, whether she is just quilting straight lines or doing free motion quilting.
If I had it to do over, I would buy a big cabinet for working with .. or get the mid-arm quilting machine and frame ...