The enemas are not causing constipation...just revealing a problem with a sluggish digestive system. This happens with colonics sometimes, too...a person may not move their bowels for a day or two afterwards...their colon is 'lazy' and not moving the new waste forward quickly. When this happens it indicates that the bowel is weaker and peristalsis slower...often because of a chronic history of digestive problems, a toxic bowel, lack of proper hydration and insufficient fiber in the diet. Cleansing the colon and maintaining adequate water intake and a high-fiber diet will help to strengthen the bowel muscle and improve peristalsis in time so that this no longer occurs.
If the p&b was working well for her she doesn't need to do the enemas...only if she becomes constipated or clogged up with a large amount of loosened plaque. The increased fiber should help to strengthen the bowel.