BrokenWings,
if ALL of her gums are white, you should get a hold of the oral sugeon. White mucus membranes can be a sign of anemia, but unless she bleed profusely, (in which case should would be in the hospital), its unlikely.

Dead tissue can be white as well. If the gums have small white areas around the surgical sites, there may be some dead tissue. When skin or other tissue swells, the outer most layer of skin or membrane often loses its blood supply. Once the swelling starts to go down, it comes off. IF you have ever had an injury that was very swollen, you might have noticed some skin peeling after the swelling went down.

The mouth is wet, and can cause small injuries to be white. Think of going into a pool with a scab on your leg. When you get out, the scab is white. Cancer sores in the mouth often have white centers.

Your safest bet though would be to call your oral surgeon and see if it is something you need to worry about or not. You don't want to take any chances of infection or other problems.

Sam