Glacyla, as she was then known:

-5'9'', which means she's not Noldorin, and probably not Vanyarin either; she's a Teler of some description.
-Blonde, which might suggest she's related to Thranduil in some way (though not closely), or Haldir (ditto).
-Green eyes. Emerald green eyes, which is unfortunate. Put that down to her being a badfic character.
-Looks about 120... but she's an elf, and I doubt Eva has any skill in judging these things. It's not like she was looking into her eyes or anything.
-Has 'cold' eyes.
-Has a violent streak.
-Is quite clearly under the influence of the Voice of Saruman. That implies... what? Saruman never became openly evil, so he's not going about kidnapping elves. Perhaps she was a member of his staff, before he turned to Sauron, and never got a chance to leave.

Did Isengard have a household staff? It's hard to imagine Saruman cooking his own meals, bleaching his own robes, running his own forges and the like, and we know he wouldn't have been using orcs before the War of the Ring (because he's not thick). So perhaps, yes, he had elves on the staff. I can't really imagine him trusting Men, though he certainly used them.

And what sort of elf would he want to... employ, for want of a better word? One from Eregion, who might know something about ring-lore. Yet Glawhatsit was being used as a housemaid, which means she didn't know about rings.

Okay, then. She was born in Eregion to parents out of either Lorien or Doriath (in both cases, having come to Eregion with Galadriel and Celeborn). Her blonde hair and unusual light eyes got her named Maedhwen, 'the pale maiden'. When she grew up, she became a warrior, and chose the name Maethorwen - because it sounds like her original name, so she was sure she'd respond to it.

She fought against Sauron's forces during the fall of Eregion, and was one of the survivors who managed to retreat to Imladris. When Numenorean aid drove Sauron back, she moved to Lindon - she wanted to live somewhere with a decent population (ie, not Imladris), and didn't want to live under tree cover (ie, not Lorien).

She fought in the War of the Last Alliance in Gil-Galad's host, and acquitted herself well. When the Noldor began to quit Middle-earth, she remained in Mithlond, and (when not guarding the city) became an adequate shipbuilder under Cirdan.

She was present in the city when Saruman's ship arrived, and despite not knowing who or what he was - he just looked like an elderly mortal - she sensed something in him: a power and skill of Craft which she hadn't seen since the glory days of Eregion. Of course, Saruman was heading east, so she could do little but watch him go.

Over a thousand years later, he returned: still looking old and worn, but with his inner power if possible even stronger. Maethorwen accompanied Cirdan to the formation of the White Council, though of course she wasn't privy to its discussions; but afterwards she offered her service to Saruman. He, already coming up with his own plans, accepted; and when, 300 years later, he took possession of Isengard, Maethorwen went with him.

From Saruman's perspective, she was something of an experiment: he was annoyed that the Eldar didn't succumb to his manipulations and his voice very easily, so he used Maethorwen to test the long-term effects of it. As it turned out, this was a reasonable success - by a combination of flattery, demeaning comments, and magic, Maethorwen ended up doing whatever Saruman wanted, though not always very happily. She mostly hid her anger and disappointment, coming across as emotionless and cold. But when she let it get out, she was still a force to be reckoned with.

I think that's a decent backstory to account for her presence in the badfic, and means she doesn't have to be yet another 'hey, pick a name for yourself' character. Good! Welcome to the DOOCH, Maedhwen Maethorwen.

hS

The word is not Sindarin, dagr is the Noldorin to the Sindarin dagor, in fact, all the names are in Noldorin. And fair enough, I don't know it's allowed in Noldorin either, and my research gave me no definitive answers.