According to Cinema Blend on Dec. 15, Evangeline Lilly spoke about how she never wanted to partake in a love triangle in Peter Jackson's "The Hobbit: The Desolation of Smaug". The film trailer seems to show Thranduil discussing how Legolas, played by Orlando Bloom, is rather fond of Tauriel who is played by Lilly. So before the movie came out, fans at least thought there was one part of the triangle in place.
Fans have discovered that this elven character is a new addition to the film version and she fights along Legolas as she takes on the orcish hordes. In fact, there was some elven jealousy in comparison between Bloom's and Lilly's daggers as well as in the fabric used for their pants. It appears that Bloom preferred Lilly's leather ensemble more than he enjoyed his own suede pants. In addition to the main story line, Lilly's character does have a sub-plot.
It appears that Tariel is torn between the dwarf Kili, played by Aiden Turner, and Legolas. Of course, Kili has been coined the term "the hot dwarf" on the Internet and he even So Kili does seem to favor intercultural romantic interests and this love triangle would make sense because he had flirted a bit with a young harp playing elf maiden during the dinner scene in the "The Hobbit: The Unexpected Journey".
Though Lilly did make Jackson promise never to have a love triangle come even close to her, situations can change and she was called upon to partake in the love synopsis anyhow.