I also agree that your wife should test drive machines and select one she likes.
Does she already own a sewing machine? If not, it is good to read some articles on what to look at when testing out a sewing machine. Bring some pieces of fabric that are typical weights of what she wants to sew and test those out. (For example, sewing denim for making jeans is different that sewing quilt weight cotton fabric.) Try out threading the machine.
Think about what features are most important. If sewing clothing, home goods (pillows and curtains) and quilts is most important, skipping the the embroidery capability gives you a lot more choices. I've seen a lot of people get embroidery capability and then hardly ever use it - I suggest making sure you can actually name a good handful of embroidery projects you want to do before buying the capability.