I haven't read it but from a quick scan of the first few chapters this appears to match quite well:
Although this was published on FanFiction on May 28, 2018 it matches in enough other aspects. For example, it is easily over 100k words at 120,899. The description of the story reads:
A girl recounts the time of her life in the First Age of Arda. She is of no House, a misbegotten child living alone on the other side of some beautiful country, and with every sorrow, the flower of shadow planted in her heart waxes, and perhaps the call of the blood flowing in her veins might at last be answered. Prequel to 'The Gift of Broken Gemstones'.
The girl is indeed a female, Noldo elf and the following excerpt implies that she ends up getting very close to a male Noldo.
I don't know how long I hid the dark shades of the trees, but it was then that a new time of my life began, for Finno found me hiding there and brought me back to the Noldor's camp in Hísilómë. I indeed must had been an odd sight—a little elf-child hiding in the bushes of a dark forest after a bloody battle; it was, in fact, the time following the Battle of Lammoth, which had taken place in the first year of what had become known as the First Age. He was an odd sight to me also, for I had never before seen another Noldo besides my mother and I, and instead of mistrusting him he became a brother to me, especially in the coming years of my life.
And this bit describes that it does indeed initially take place when the Noldor flee Aman for Endor.
"I was there on the day of the festival when the oath of Fëanáro was sworn, and I followed my father as he came with Fëanáro and much of the Noldor here to Endor. I was unsure of what I should do at the time; Fëanáro was a very convincing Elda—manipulative, almost. After Finwë's death he gave a passionate speech, and nearly all the Noldor followed him, fleeing Aman for Endor. Atarinya told me he didn't want to abandon the people to Fëanor, and that was why we were leaving also. But my mother Anairë would not leave with us. Yet here I am, on the other side of the ocean, far away from Valinor."