Itaril

[Pitchwife]

Welcome to the Downs, Peterson_Hobbit!
The Shibboleth of Fëanor gives Itaril (or Itarillë) as the Quenya form of the name Idril, Turgon of Gondolin's daughter, who married Tuor and became Eärendil's mother. Like Inzil has already said, she has no part whatsoever in The Hobbit.

A quick google search of "Itaril hobbit", however, revealed this:

Originally Posted by http://collider.com/casting-info-for-the-hobbit-revealed/13531

[ITARIL] FEMALE, A WOODLAND ELF, this character is one the Silvan Elves. The Silvan Elves are seen as more earthy and practical. Shorter than other elves, she is still quick and lithe and physically adept, being able to fight with both sword and bow. Showing promise as a fighter at a young age, ITARIL was chosen to train to become part of the Woodland King’s Guard. This is the only life she has ever expected to live, until she meets and secretly falls in love with a young ELF LORD. This role will require a wig and contact lenses to be worn. Some prosthetic make-up may also be required. LEAD. AGE: 17-27. ACCENT – STANDARD R.P.

So it seems like PJ & Co. nicked the name for some token female Elf who wasn't in the book either, but whose presence is presumed necessary in order to feed the unwashed movie-watching masses' hunger for on-screen romance. I'm afraid it takes no extraordinary sagacity to guess who the "young Elf lord" she falls in love with is going to be... *shudder*