Here are a few resources you can look at concerning NPD treatment prognosis:
Ogrodniczuk, J. S., Piper, W. E., Joyce, A. S., Steinberg, P. I., & Duggal, S. (2009). Interpersonal problems associated with narcissism among psychiatric outpatients. Journal of Psychiatric Research, 43, 837– 842.
Pincus, A. L., & Lukowitsky, M. R. (2010). Pathological narcissism and narcissistic personality disorder. Annual Review of Clinical Psychology, 6, 421– 446.
Gabbard, G. O. (2009). Transference and countertransference: Developments in the treatment of narcissistic personality disorder. Psychiatric Annals, 39, 129 –136.
Campbell, W. Keith and *****, ***** (2011). Handbook of Narcissism and Narcissistic Personality Disorder. John Wiley and Sons.
REICH, JAMES H. M and VASILE, RUSSELL G. (1993). Effect of Personality Disorders on the Treatment Outcome of Axis I Conditions: An Update. Journal of Nervous and Mental Disease, 181.
Stone, Michael H (1993). Abnormalities of Personality: Within and Beyond the realm of treatment. Norton and Company.
Unfortunately as much as you "love" this individual, the reality is going to be the same as most likely this individual will not change and because treatment is voluntary, most patients with NPD will consistently not follow through with treatment. So it is not about what focus a mental health practitioner has because if the individual will not abide by treatment than there is not much anyone can do...as a comparison if an obese patient has been told by their doctor to exercise and eat right, but will not, there is little a medical doctor can do. The same applies to mental health treatment because 95 percent of the effort is made by the patient