Please understand that nurses can only dispense drugs for pain according to the doctor's orders. Some pain meds are very addicting. Others can kill a patient if given too often or in too high a dosage. Pain management is often a difficult part of patient care. This is especially true for someone like your wife who already has constant or chronic pain.
Sometimes it's difficult for the doctor, nurse, or other health care worker to judge a patient's pain level. Seeing pain and suffering on a daily basis can decrease the observer's sense of understanding or empathy. The health care worker's own distress may actually reduce his or her empathy as a way to cope. Studies show this is a common response in critical care and burn units.
Talk with the nurse in charge and/or the doctor. Having a better understanding of the big picture may help both you and your wife cope. On the other hand, your questions may help the medical staff review pain measures being used with your wife. It's possible there's a better way to manage her case.