Maybe it is possible. But I do see what you're saying. However, I don't really think it's any of your business to be telling her what she's doing wrong. He obviously likes her and if she's willing to put in the effort to learn to "love him", then that's up to her.
In my opinion, even when you're in a relationship ; you still look. In all honesty, who doesn't? You meet another person and you think "Yeah I can imagine being with them" etc, or "they seem nice", it's only natural to have thoughts like that, it's not necessarily dishonest or wrong because we can't help the way we feel.
If she was to cheat on him, then maybe I think you would have good reason to say something to her! But it's her life and her loss if she loses this guy due to her dishonesty.
You don't have to agree with her, but she is your friend - so remember that. Jealously is ugly and you shouldn't be so worried about the type of guy that you never get. Maybe the reason you don't get the guy you want is because you take second best. I dunno.
To love is to suffer. To avoid suffering, one must not love; but then one suffers from not loving. Therefore, to love is to suffer, not to love is to suffer, to suffer is to suffer. To be happy is to love; to be happy then is to suffer, but suffering makes one unhappy; therefore to be unhappy one must love or love to suffer or suffer from too much happiness. I hope you're getting this down.