Sure, you could pay someone $200 to fit your wife to a bike... that will definitely work.
Or, do like 99.732% of riders and just do some tweaking on your own. We'll all be in the orthopedic ward together in a year or two I am sure...
You may want to take the time to measure, and do an "online" fitting:
http://www.competitivecyclist.com/za...LCULATOR_INTRO
I am a fan of the French Fit for a casual cyclist.
Make sure that the measurements from crank to saddle and saddle to bars etc are in the right ballpark. Any fitting, whether online or professional, unless it is for pure performance and involves wind tunnels etc is only enough to get into the right ballpark. After putting in some miles, the rider is the best judge of whether a small tweak needs to be done. Even if everything is by the book and looks perfect if a rider feels too stretched out, then guess what? They are too stretched out.
Even if her bike is slightly outside the suggested size you may be able to adjust with the right stem and/or seatpost, as it seems you realize. If it is too far outside, you probably need to get her a more suitable platform to start with.
If this fails, then you still have the option of a professional fitting.
Also, your wife (like me) probably needs to work on her core muscles in order to ease the stress on her upper body and arms, and as suggested, she needs to learn to keep her elbows slightly bent. She would probably be more comfortable with her elbows bent with some arm strengthening work too.