[Pitchwife]

First of all, if we keep the name Tauriel (which I have no objections against, at least it has the advantage of being well-formed Sindarin), there must be a reason she's named so - i.e. someone called Forest-daughter must have some more special connection to the forest than just being one of many many female denizens of Mirkwood. Coming from this consideration, I could see her as a sort of Nellas figure - a young girl at home in the forest (and by all means dancing merrily in moonlit glades), but not so much in a crowd of people gathered in the king's hall. What part such a character could play in Bilbo's story (other than being frightened by the Dwarves) is another question which needs further rumination.

As another possibility (abandoning the name) I could see a serving maid of Thranduil's court who somehow discovers Bilbo's presence during his stay in the Elvenking's fortress, but pities and befriends him - maybe even helps him to free the Dwarves? Let's say she's the one who delivers water and bread for the prisoners down to the dungeons. It would be even nicer if they never actually spoke a word, but she finds a way to let him know that she knows about him - an occasional morsel of food and a cup of wine left for him here and there, a gesture pointing him in the right direction to find out where Thorin is being held, something along those lines.

Finally, picking up Formy's point about Thranduil being basically Thingol 2.0, why is there no Melian at his side? Knowing Elvish Laws & Customs, he must have been married in order to have a son, and I can't at the moment recall any text saying he was widowed. Give the Elvenking a Queen, and make her as different from Galadriel as it gets (e.g. even more anti-Dwarves than her hubby), et voilà.

I like the serving maid best, but any of these would IMO fit TH better than Arwen Reloaded falling in love with Orlandolas. The Hobbit has no romance, The Hobbit needs no romance!