Winter the Shapeshifter

Winter is a teen in high school, living out in the country on a ranch.
One day she sees a horse in a pasture
on a pleasure walk. It seems like it's sucking her in, pulling her.
She feels pain, like someone is twisting and stretching her, hen it's over. She's a horse.
She enjoys her new talent of running through the meadows at first, but it soon becomes hard to conceal. How will she do it? And that's when she finds she can be other animals, too. Will that make it easier? Or harder...?