It's going to come down to what your wife wants and that may not correspond to what you want to buy for her.
If she wants to go shopping with her bike then look for one that comes with a rack or has mounting points for one. Fenders may be something she wants too. If the gearing is pretty much the same as your bike, and all other things being equal, she should be able to keep up with you if you ride together on an excursion/outing.
Usually more expensive bikes come with better quality components, but you would have to compare side-by-side the specs. Proper fitting, assembly, and tuning by the LBS will ensure immediate biking enjoyment regardless of the bike you end up purchasing.