Nah, thats just how their arms look when they aren't fighting. Coiled up.

I guess because of the style of the video its just hard to see the lines showing the spiral of the arm.

In the video, she has regular arms. There's a close up of her hand grabbing the letter, and there are no lines at all. plus, her arms start out as the same color as her skin, as opposed to the pale yellow of her hair.