If another woman than your partner is the woman of your dreams, then why are you with your partner?

It's one thing if he sees another attractive woman. Can't expect him to wear a blindfold for the rest of his life. It's another if he starts drooling over her and feels she's his dream woman.
That's the end of the relationship as it means he's not feeling it for me anymore.
As long as I'm his dream woman, pas de problem as long as it's respectful.
I mean, I also see other attractive men, can't be helped. Doesn't mean you have to be immature and disrespectful towards the one you love. After all, I chose him, and he should be able to trust I want him and only him, even when Adonis himself walks by. And he has to be able to trust that I won't humiliate him. Simple matter of maturity.
Those feelings and trust should be mutual. Without that you have nothing to build a relationship on.