Varda&Melkor and Marriages of Valar

[Earendilyon]

Thinlómien, I quote a somewhat longer text piece of the Silm regarding Varda:

With Manwë dwells Varda, Lady of the Stars, who knows all the regions of Eä. Too great is her beauty to be declared in the words of Men or of Elves; for the light of Ilúvatar lives still in her face. In light is her power and her joy. Out of the deeps of Eä she came to the aid of Manwë; for Melkor she knew from before the making of the Music and rejected him, and he hated her, and feared her more than all others whom Eru made.

I think especially the first part declares a lot: Varda delights in Eru's light and it lives still in her face. Melkor hated light (especially Eru's Light) and loved Darkness. I think Melkor tried to sway Varda to his side (like he did with Sauron and many other Maiar) as she was a very powerfull Vala; with her help, he thought he would certainly overcome the other Valar. This she rejected (you used the right word in your translation!); she didn't want to be part of his schemes as she delights in the opposite of what his delight is: Light vs. Darkness.