Narcissism is not really the correct term to use. Narcissism is love of oneself, what CDs develop is autogynephilia which is the love of the image or idea of themselves as a female. As such CDs are attracted to a fantasy concept not actually with themselves and much of that attraction is based upon the automated sexual response to visual feminine signals that we are conditioned to react to.
All heterosexual CDs will develop autogynephilia to some degree because we are all responding correctly to what we are supposed to find attractive. The struggle is to realize this is occurring and to stay focused on your partner and not on a fantasy.