When you look at your wife's feet, see the body in it. Everything on the feet follows the body from toes to heel. The tops of the toes are brain points, the heels are your intestines and colon. The point where your foot makes a "point" between the arch and padding is your solar plexus. Just below that is your stomach/kidney area. Always always always always massage in a clockwise direction, that will help release the toxins and get everything flowing. I would massage the stomach area AND the intestines to get things moving. I hope this makes sense...I will refer a site that maps out the foot! Hope she feels better!
Additional Info: To the person who says massage therapists are not reflexologists...many of us are trained in reflexology because it IS a form of massage therapy. There are so many different forms of massage, it's impossible to limit yourself to just one technique. In every massage I do, I incorporate the feet. The benefits of working the feet are numerous. The person below me has a wonderful answer, she is definately right in that water is a huge part of releasing toxins.