I do like this drabble, it is sweet and somewhat dreamy. I find the comparison between Luthien and Nimloth wonderful and I always enjoy reading lesser written about characters and pairings.

 As for concrit I will admit that in "her hair so dark, her skin so fair"  the double 'so' felt a bit overdone in my opinion although I can see the effect you are aiming for. I also admit that reading that sentance seem to imply (to my currently sleepy brain) that Luthien's hair was not as dark nor her skin so pale as that of Nimloth's which seemed att odds with how luthien is always described.

 Anyway very enjoyable :)

I have been imagining the meeting between these two recently (for my own purposes of course), and I had not thought about what the son of the most beautiful woman to ever live would look for in a wife.  Interesting take :)