Vin,
Agreed that scanning is a good option to see if there's a reason, such as a blockage,for the infection. Even without flow, salivary glands do not usually get an infection that is not treatable. Change in antibiotics is also a good suggestion, especially if an organism can be cultured from the infected gland.
Irrigation of the gland is possible (by your oral surgeon or ENT) by using the small ductal opening in your mouth. If an obstruction is there, it can be flushed out. Some people have inflammed parotid ducts that can be helped using a steroid irrigation. As Brian suggests, the best idea would be to find out why or what organism is causing the inflammation and pain.
Hope things improve for your wife.