Obviously she is under the care of a midwife or doctor and she should make sure that it is not a symptom of something which needs addressing. Generally, cutting down on sugar, salt and caffeine and drinking more water will help to encourage the body not to retain. Mechanical drainage can help, if its in the legs, rest and sleep at night with the feet higher than the hips, if in the hands spend some time with the hands supported higher than the elbow. gentle massage of the limbs and wiggling the fingers and toes can help to encourage the fluid to move back to where it should be. Don't spend too long on your feet at any one time and try not to stand still, either sit of fidget from foot to foot. The problem does tend to disappear when the baby appears. Be very careful about getting bruised or scratched in the oedematous areas as they will take longer to heal and are more vulnerable to infection, this can mean being careful around household pets as they all have dirty claws!!