it's rather sad,isn't it Mr Veritas......she is 'suffering' from a crush,and one hat will soon be defined as 'unrequited love if she continues in the same vein. I think for the time being,you may be best off leaving her to it. maybe a further discussion about how he is what he is,and nothing can or will change things will help. But there is little that you can do. If she insists on trying to change him-THEN more drastic action may be necessary. Just leave her be for now...I think she will soon face up to what may be a slightly painful reality.
Lets face it...she has known this guy all her life-they have essentially grown up together. He is or may be the dominant young man in her life,and she may not have realised until now just how important he is to her. Up until now she has had his full attention. She is afraid of losing him...even tho she won't.