I must confess that I, along with, I'm sure, scores of other female Hobbit fans, am a huge fan of the Tauriel-Kili relationship.
Sure Tauriel is an elf and lives with the apparent heart-throb Legolas, but he is kind of standoffish, and his dad is fairly nuts, and then there's that whole class thing.
Along comes this attractive dwarf who teases her and talks poetry to her and just, well, talks to her (not at her or about her). On top of all that, he is completely captivated by her from the get-go, impressed by her warrior abilities.
Still, it's the talking to her that impresses me. I mention in my Boromir post that in only a few scenes, Jackson is able to establish that Boromir is a good guy and liked by the hobbits. He does the same thing in The Hobbit: The Desolation of Smaug with Tauriel and Kili when they discuss the stars and Kili begins to tell Tauriel about his travels. Their easy relationship, their interest in the same things, in each other, is almost instantly established.
She takes the kingsfoil. Bofur says, "What are you going to do?"
"I'm going to save him," Tauriel says.
By themselves, the words could be meant arrogantly or passionately, but Tauriel (Evangleine Lilly) says them like she's found a purpose in life or, rather, like she has found a reason to be a elf. *I* can do this. *I* can do something for him that no one else can. I was right to come.
I have my own opinion about what will happen next (taking the book's ending into consideration) and how all of it will affect Legolas. And I think this is one place where a director's invention is completely merited. Tolkien doesn't give us much on Legolas to explain his background or motivations. Jackson and his fellow scriptwriters have gone a long way towards filling in the gaps.