Silmarillion - Chapter 22 - Of the Ruin of Doriath

[King Naugladur]

Originally Posted by Inziladun

It seems the withdrawal of the Girdle was not a conscious act by Melian, but a symptom of her emotional and spiritual despair at the death of Thingol. Knowing that she was, either temporarily or no, incapable of doing anything herself to recover the Nauglamír, she did what she could to stop the Dwarves.

To me, it seems that Melian returned to Valinor in order to mourn her husband's death and possibly plead for his release from Mandos. After all, Melian was a Maia. She could have waited for Beren show up with his host or the war between Nogrod and Doriath end in one way or another and then go and mourn for her husband.

Originally Posted by Inziladun

The Ents would have been close to the Green-elves, and the latter likely told them what had happened in Doriath.

Quite a good explanation, Inziladun.
King Naugladur.