I would recommend a belt-drive bike because it's a whole lot cleaner and much less maintenance. Here is a $599 Priority with a 3 speed hub:
BTW, don't just assume your wife would ride a step-thru town bike. A lot of women are deadset against this type of bike because it makes them look old and dowdy. Just as a lot of women actively resist minivans because it makes them look like soccer moms (especially true for actual soccer moms). So make sure she is OK with this type of bike first.