Thuringwethil

[Macalaure]

Originally Posted by Lalwende

The 'skin' of Thuringwethil is clearly a bat-like shape, and it must also have fit human/elf form if Luthien was able to wear it and be so well disguised. I don't see much here to detract from the 20th century image of the vampire - a human form with bat wings.

Since Draugluin evidently didn't have human/elf form, I don't think Thuringwethil necessarily had to. She maybe roughly had the same size, in order for Lúthien to fit in, and the rest is left to 'the arts of Lúthien' - however we may exactly picture this.
Given the few information we have about her (your two quotes are all we have, if I'm not mistaken, so we don't even know how she died!) we seem to be quite free to imagine her in whatever way we want.