This may not be what you want to hear, but I think you should just react kindly. Sure she may hurt you and make fun of you but secretly she might be going through a hard time and need you most. Maybe not though, and maybe she's just being mean and spiteful. Even so, be as kind to her as possible. Your example might change her attitude. When my sister's like that, it helps me a lot. And when I respond to her like that, I help her in return.

*Offers a hug* I hope things get better!