This is easily on Parr with Twilight, Fallen and the Selection. Utter tripe. It was a good idea but the execution was painful and uninspiring.
I wanted to grab Helen and shake her by the shoulders screaming "GO BACK TO NURSERY YOU SPOILT, PETULANT LITTLE CHILD!" She was so immature it was infuriating. Oh, and she's a special Mary Sue too. The most beautiful, the most powerful, the fastest, the freaking best at everything and INDESTRUCTIBLE. Seriously. Now let me go puke...
The characters, all of them, were very flat. They feel as though they've been given only just enough to be classified as a character rather then a name on some paper, but no more. As though by adding some depth would have been a curse. This makes the story even more flat and shallow and DULL.