@ the OP
It is tough to know how to deal with those thoughts and feelings all people have. Should we tell others what we're thinking, knowing full well those thoughts will cause pain to the other?

I don't know that you should beat yourself up too badly. You were trying to be honest with yourself and with her. If you don't want to date someone who is overweight, there is nothing that says you must.

I don't know that what you describe is narcissism, but I'm not a mental health professional, and only they can make a diagnosis.