I think she says more like:
Silent she comes through the night
Desiring a silver light
Leaving with dusk in her eyes
Descending from paradise
Desiring sounds more logic than any mention to a siren. And it fits better the rest of the paragraph.
By the way, there's another part of My lost Lenore that I can't figure out. The girl whispering after the first choir from Morten... and just before "grieving raveneyes..." so if anyone knows what she says, I'd appreciate it. <_<