Would Aewen+wen ("maiden of the birds"; i.e. she hangs out with birds a lot) just be Aewen? Or would it elongate the wen part back to wendë becoming Aewendë? Except Sindarin doesn't have wendë does it? Aewengwend?
Essentially from what I can tell it would be Aewenwen. Because S. gwend, n. “maiden, *young woman” root is √WEN(ED). Which seems odd to me. But I will defer to others though.
lol Well it will be an interesting trip if that's her name. Why did you drop the e from Aew?
Aewenwen might technically be possible as a very late compound, cf. Angrenost (but this one uses a different suffix, so it is shaky evidence at best). Aewinwen may be slightly more correct. I would not recommend either though, they sound terrible and are quite uncertain...
Reversing the elements might offer a better solution, Gwennaewen, though still a bit of a mouthful.
"Bird-maiden" might ultimately be better. To avoid it becoming identical to aewen (the adjective) I would retain a longer form of the suffix, Aewenn or even Aewend. Or reverse the order of the elements, Gwennaew.