This sounds rather interesting. I hope you'll continue this story.
Is Elsa hunted down because of her ice-powers?
I really wish there's going to be more.

I hope you do get a chance to continue this story. The questions raised in the first chapter certainly piqued my interest. What has Elsa got herself involved in that means an assassin has been hired to kill her? Does she still have her ice powers? What roles do Ralph and Vanellope and Felix and Anna and Kristoff and Hans have in this tale?

The one thing I would say is that you have quite a long paragraph in which Tamora stalks Elsa and then sees her get shot, and it really needs to be broken up into shorter sections. Long paragraphs are fine when the pace is slow, such as when you tell us Tamora's backstory, but such an action-packed scene as this ought to be punchy and coherent. Just a tip for further chapters.

This is a great idea for a first fanfiction! A relationship between Tamora and Elsa has never been done before (as far as I can tell), so this should be good. Don't give up!