The usual Quenya word for “maiden” derived from the root √WEN(ED) (Ety/WEN; PE17/191; VT47/17). Tolkien usually wrote this word as wende but it would be pronounced and written vende in modern Quenya.
Conceptual Development: This word was fairly stable in Tolkien’s mind. In the Qenya Lexicon of the 1910s this word was ᴱQ. ’wen (wend-) “maid, girl” with longer variant wendi “maiden” derived from the early root {ᴱ√WENE >>} ᴱ√GWENE (QL/103). The form wendi was also mentioned in the contemporaneous Gnomish Lexicon, but there the root was {ᴱ√gw̯ene >>} ᴱ√gu̯eđe (GL/45). In the Nieninqe poem written around 1930 it was ᴱQ. wende “maiden” (MC/215), a form that reappeared in the version of the poem from the 1950s as well (PE16/96).
In The Etymologies of the 1930s Tolkien gave this word as ᴹQ. wende, vende “maiden” under the root ᴹ√WEN-ED of the same meaning (Ety/WEN), In a marginal note Tolkien said that derivatives of ᴹ√WEN-ED should be transferred to ᴹ√GWEN, and under that root Tolkien indicated there was blending with ᴹQ. wende “maid” (Ety/GWEN).
In later writings Tolkien mostly used the form wende, but in Quenya prayers from the 1950s he once wrote Vénde, where the long é was probably a slip (VT44/5, 10). Likewise in later writings Tolkien mostly gave the root as √WEN(ED), but in one place considered deriving wende from √GWEN “fair” (PE17/191). Finally he generally translated this word as “maiden”, but in Quenya Prayers from the 1950s used it with the sense “virgin” in reference to the Virgin Mary (VT44/5, 12).
Neo-Quenya: It is tricky to reconcile Tolkien’s regular use of the form wende with the root √WEN(ED), since ancient *w* became *v* in Quenya, making the expected form vende. To retain wende, the most straightforward explanation is that it was derived from strengthened ✱gwendē, since this initial cluster survived as *w* at least into Classical Quenya and possibly beyond. However, the strengthening of ✶wendē > ✱gwendē must have occurred after the Common Eldarin period, otherwise the Sindarin form would have been ✱✱bend, whereas Tolkien consistently used S. gwen(d).
Many Neo-Quenya writers avoid this question simply by revising the form to vende, a practice I recommend as well, though its suffixal form would (mostly) remain -wen. I also prefer to use vende mainly for “maiden, ✱young woman” and for “virgin” (of any gender) I recommend vénë.
wendë noun "maid" (GWEN), wendë > vendë "maiden" (WEN/WENED, VT45:16, VT47:17). Sana wendë "that maiden" (PE16:96 cf. 90). According to VT47:17, this word for "maiden" is "applied to all stages up to the fully adult (until marriage)".Early "Qenya" also had wendi "maid, girl" (LT1:271); this may look like a plural form in Tolkiens later Quenya. On the other hand, VT48:18 lists a word wendi "young or small woman, girl". It is unclear whether this is Quenya or a Common Eldarin form, but probably the former: PE17:191 displays the word for "maiden" as wendē, so the Quenya stem form is probably *wende- rather than wendi*-, the stem-form that would result from Common Eldarin wendi). In his Quenya translation of the Sub Tuum Praesidium, Tolkien used Wendë/Vendë to translate "virgin" with reference to the Virgin Mary. Here the plural genitive Wenderon appears in the phrase Wendë mi Wenderon "Virgin of Virgins"; we might have expected Wendion instead (VT44:18).If the pl. form of wendë is wender rather than wendi, as the gen.pl. wenderon suggests, this may be to avoid confusion with the sg. wendi** "girl".