The doctor and therapist are the best ones to answer this question. Ask the therapist this question again after he or she sees your wife and makes a full examination. Once a week visits for injuries of this kind is common in a prepaid health care plan. Older injuries are allowed even less frequent treatments.
The therapist will probably instruct your wife in ways to manage her pain at home. Self care and exercises are common ways to treat patients who have limited time with the therapist. It may be possible to petition the health care administrator for more visits if the doctor and the therapist think it's needed.
You can also always pay out of pocket for more visits. Most clinics are willing to work out a payment plan that meets your financial needs while also meeting your wife's physical needs.