I think I have my sindarin picked out rightly, just need help properly combining the roots and forming the name.
So...
Lang+dress Taur+acharn
"Blade-Girl of the Forest's Vengance" is what it's supposed to be. Am I right so far? And what does that look like all put together?
And while we're at it is there any word on how long it takes for elves to reach physical maturity? Is that the same as humans or greatly exaggerated? I'm assuming they don't pop out fully formed.
Wow. You want a complicated one.
Lang is one of four words for sword, hathel is blade. Gwên is girl (or virgin), iell and sell are also girl. There is no dress. Taur and acharn are correct.
The definition construct would end up being "Girl of the Blade(sword) of the Vengeance of the Forest" or as you shortened it, "Blade-girl of the Forest-vengeance."
The first part could be: Hathelwen, Hatheliel, Hathelsel, Langwen, Langiel, Langsel, Cristwen, Cristiel, Crissel, Magolwen, Magoliel, Magolsel, Megilwen, Megiliel, Megilsel
The second part would be: Torachar
In order to get the full definition it would inlcude en or uin (of the) between the parts (i.e., Langwen en Torachar or Langwen uin Torachar. However, for a name I would drop it and just use one as a first name and the other as the surname, as I'm sure you were intending.