No she didn't. Tolkien re-wrote her story a few times, and she is a late addition to the myths. In one passage > Galadriel, the only woman of the Noldor to s

No she didn't. Tolkien re-wrote her story a few times, and she is a late addition to the myths. In one passage > Galadriel, the only woman of the Noldor to stand that day tall and valiant among the contending princes, was eager to be gone. No oaths she swore, but the words of Fëanor concerning Middle-earth had kindled in her heart, for she yearned to see the wide unguarded lands and to rule there a realm at her own will. Which doesn't say she was part in the kinslaying (though it doesn't say she wasn't, but its hard to interpret "Standing tall" as "participated in slaying her mother's kin"). In another version > Even after the merciless assault upon the Teleri and the rape of their ships, though she fought fiercely against Fëanor in defence of her mother’s kin, she did not turn back. Her pride was unwilling to return, a defeated suppliant for pardon; but now she burned with desire to follow Fëanor with her anger to whatever lands he might come, and to thwart him in all ways that she could. Which sounds like she participated _against Fëanor_, as in: she defended those being attacked. In another unfinished version she left Valinor on her own separate from the rest of the Noldor. In any case, she seems to be motivated by a desire to rule her own realm and a strong dislike of Fëanor. Also, I am fairly certain that Tolkien was writing a fairy tale when we wrote about Galadriel and co. :)