Melian's Change

[Maédhros]

After Thingol died, why was Melian changed. Why were her powers diminished?
But now Thingol lay dead, and his spirit had passed to the halls of Mandos; and with his death a change came also upon Melian. Thus it came to pass that her power was withdrawn in that time from the forests of Neldoreth and Region, and Esgalduin the enchanted river spoke with a different voice, and Doriath lay open to its enemies.
Was it the Power of Love? Was it Morgoth's power that had become greater? Was it a design of Manwë?
Why did she abandon her people?
Thereafter Melian spoke to none save to Mablung only, bidding him take heed to the Silmaril, and to send word speedily to Beren and Lúthien in Ossiriand; and she vanished out of Middle-earth, and passed to the land of the Valar beyond the western sea, to muse upon her sorrows in the gardens of Lórien, whence she came, and this tale speaks of her no more.

[Naaramare]

I don't think she lost her powers, she just pulled them out of Middle Earth. ME had become a home for her and Thingol. With Thingol dead, she had no more interest in ME--indeed, no more interest in anything at all. The power she'd infused into Doriath she took back and then she went to Aman.

[Maédhros]

With Thingol dead, she had no more interest in ME--indeed, no more interest in anything at all.
Didn't she cared about her people? I think that she should have done more to help them.

[Naaramare]

She did. She handed them over to the governance of her daughter and daughter's husband.

She was broken, in a way, by Thingol's death, and I think it was probably for the better. I don't think she would have been much of a leader.

[Orofacion of the Vanyar]

I believe a union of this nature, of high elf and maiar, is something more than just a marriage. I believe Thingol and Melian were connected at the spiritual level, not just the physical. This would mean when Thingol was slain, that connection was broken and the power was recoiled. Think of it like this: Thingol and Melian's union was a chain that bound all of Doriath. Once half of this chain was broken, then the rest of chain would fail, and the protection fall with it.

[Amarinth]

agreed, orofacion.

i don't have my silm with me but also from what i understand contextually of their union, melian through such a spiritual bond had invested into or at the least shared with thingol some of her power and wisdom. by this bond thingol the elf was able to rule the great elf-kingdom of doriath; melian the maia shared that rule and with her native powers protected doriath with her girdle. when thingol died i understand she had to withdraw both rule and power because the former was not principally hers and this invalidated the application of the latter. the ainu are destined to rule over the kingdom of arda, not the kingdom of elves. doriath did not begin its ruin at melian's withrawal but rather at the death of thingol, the doom of its ruler.

admittedly this dwells a trifle too much on technicality, but that's how i understood it from the very beginning.

[akhtene]

I don't think she lost her powers, she just pulled them out of Middle Earth.
Perhaps this act was of the same nature as with Luthien and Arwen. With their men dead they both chose to die too. Melian being a maia perhaps couldn't die, so she just diminished (?) and left.