Tolkien's final First Age timeline

[Galin]

Originally Posted by Huinesoron

Galadriel is meant to be 20 in "relative years" at the beginning of the Exile, which I take to mean the death of the Trees. ( . . .) Yeeeeeah... assuming Feanor creeped on her before he was banished to Formenos, she would have been "relatively" 7-10 years at the oldest. I hope she kicked him on the ankle.*

I think the idea that Feanor asked Galadriel for her hair only shows up in The Shibboleth of Feanor however, which is later than any 1959 text (in GNOME), or even Elvish Ages and Numenorean, dated to 1965.

*Actually, "The Shibboleth of Feanor" [HoME XII] kind of agrees with this! "From her earliest years she had a marvellous gift of insight into the minds of others, but judged them with mercy and understanding, and she withheld her good will from none save only Feanor. In him she percieved a darkness that she hated and feared..." Yeah, Uncle Feanaro was Galadriel's personal childhood nightmare, and then he came over and started trying to steal her hair - little "Man-maid" definitely kicked him on the ankle.

In your chart linked above you've got Feanor making the Silmarils before Galadriel was even born -- okay, based on NOME texts . . .

. . . but in The Shibboleth (1968 or later), Galadriel was born in the Bliss of Valinor (which includes the vague addition: "it was not long in the reckoning of the Blessed Realm, before that was dimmed") and the Eldar said that her hair had snared the light of the two trees, and many thought that this this saying gave Feanor the idea of blending the light of the Silmarils that later took shape as the Silmarils: "For Feanor begged three times . . ."

My interpretation is that Feanor begged for her hair before making the Silmarils. And if so, thus, in what "mode of thinking" was Tolkien involved with here, in 1968 or later? Noting too, that in another late text, Eldarin Hands and Fingers:

"nette meant "girl approaching the adult" (in her "teens": the growth of Elvish children after birth was little if at all slower than that of the children of Men). The Common Eldarin stem (wen-ed) wendé "maiden" applied to all stages up to the fully adult (until marriage)."

JRRT, from Vinyar Tengwar 47, texts generally dated 1967-70 (reproduced in NOME as well)

Carl Hostetter then refers the reader to XVI where Tolkien notes that the Elvish growth rate from conception to maturity should be comparable to Humans, with Elves reaching maturity at 24 loar (Sun Years), and in which, with respect to later weddings in the "Early Years" before the March, the Elves were usually 24/21-24 [granted CFH also refers to Elvish Ages and Numenorean too, but this text still pre-dates the "nette remark"].

In other words, I don't think we necessarily have a text in which Feanor begs a notably young Galadriel for her hair, as by the time the idea arises, we don't know where Tolkien was with respect to certain earlier notions or dates.