We were given a newly created character by the name of Tauriel. She is described by Peter Jackson as being a true Sylvan Elf, with her name simply meaning ‘Daughter of Mirkwood’. Aside from the assurance she will not have a romantic link to Legolas, we currently know nothing else about her. So, let the speculation begin.
We know in the book that we see many of the Mirkwood Elves, named or not, at a few different points in the story. First are the evening Elven campfire meals that draw the Dwarves off the trail as they follow the firelight into the forest, which then causes the Elves to vanish. After numerous such incidences, the Dwarves are finally captured and imprisoned for ostensibly being a menace to the Elven citizens of Mirkwood. Second are the various Elves involved in maintaining the Dwarves imprisonment, be it guards, those bringing meals, the Elves preparing the wine barrels and Thranduil and his entourage during questioning of the Dwarves. The Third instance will be when Thranduil decides to go to the Lonely Mountain to make a possible claim on the Dragon treasure and is involved in the Battle of 5 Armies.
The first instance doesn’t really give much face time to see and get to know any particular individual, since the visions of the Elven party are supposed to be somewhat ethereal. They appear and disappear rather mysteriously to the Dwarves, and I imagine it will be filmed that way, rather than we viewers getting a solid look at the party. While Tauriel may be amongst this party, for recognition’s sake, I don’t believe we will get a specific view, much as Frodo and Sam simply watched the Elven party parade by in the FOTR extended edition.
Once the Dwarves are captured, is a much more likely time to meet and get to know Tauriel. One possible storyline might simply be that in order for Thranduil to justify imprisoning the Dwarves for menacing the Elven party, there must be a complaint from the Elves stating they were menaced. This would be a simple way to introduce her character, in a manner that does not affect the existing storyline. As the imprisonment continues, she may be present during the questioning of Thorin, or not. Or she may at least be consulted on how long they should be punished, or not. This would impinge more on Tolkien’s original story, but then, in film, it is often seen that a leader has attendants to speak with, or at least speak to, while contemplating big decisions. We saw Theoden consulting many people in his war room, with Gamling being the main attendant. So Tauriel may end up simply being used as an expository character in this particular instance.
Of course, there is then the third instance of Elven involvement, the Battle of 5 Armies. With there being a whole host of Elves fighting, the filmmakers will want at least one or two Elves to be familiar to the audience, so the audience can invest feelings for someone during the battle. This was Haldir in TTT, who dies, along with most of his host, regardless of the fact that Elves did not go to Helm’s Deep in the book. I know this change of taking a host of Elves to Helm’s Deep and killing off a character that didn’t die in the book because he wasn’t involved in said battle created a bit of backlash. So with Legolas added to the film and Thranduil being more fleshed out, and neither of them dying during this battle, my guess is whatever other Elf appears for us to get to know, probably will die. If Tauriel is the only other Elf we really get to know, I fear her fate may well be sealed. After all, battles are messy and there will need to be sacrifice on all sides of the allied armies to balance things out.
But all of this is merely speculation and Tauriel might simply be an Elf maiden who prepares meals for the captured Dwarves. Or maybe she is just a wine maker preparing the barrels for their trip downstream to Laketown. With the very little information we have for Tauriel, there is no way to know if she is onscreen for just a few minutes or if she will feature heavily in much of the Mirkwood Elven storyline. We will just have to wait and see if Tauriel is a warrior, a scout, a winemaker or a guard, because for now, all we know is her name and that she won’t be romantically involved with Legolas.