You have to remember that they need some T&A in these movies...hence Liv Tyler having way too big a part in Lord of the Rings.
Um, okay, no, I finally have to say something lol Arwen was not included in LOTR for T&A. She is not naked in any scene and is never, EVER presented as a sex object. EVER.
Arwen is not even IN the original novel(s). Why, because Tolkien simply did not think to write about women. Women had a place in his life, and that was in the home. It was the 30s/40s/50s, and he was very old-fashioned. So that is reflected in his work. Even Eowyn only goes to battle to be with her "love" Aragorn and ultimately gives up her sword and shield to become a "healer" once she finds her "proper" love.
Jackson and co. increasing Arwen's visibility in the narrative AND altering Eowyn's motivations AND including Galadriel in The Hobbit AND creating Tauriel were done as service and acknowledgment towards FEMALE fans. Because the original narratives are essentially boys' stories, stories about boys going on journeys and having adventures WITHOUT women. I am grateful to him and his team for what they have done; they really thought about appealing to female fans and making them feel included; they wanted to show that women can go on adventures just like men can.
The only issue I have with Tauriel is the love story... in my opinion, in order to be a well-written female character (not just a trope) she needs more motivation than a boy she just met to leave her home for the first time. But ultimately I think her character was handled well and the actress did an excellent job.
Just my two cents on the matter; could not stay silent any longer 
BACK TO CULLEN....