Remember, when someone torments you, it's the reaction they are looking for. When you throw something, your sister won! The hardest thing in the world is to stay calm when someone is annoying but it's also the most effective. You need to rise because she will not change if you don't.
I always believe that every experience in life is there to teach us something or shape us--maybe make us better if we can grow from it. My suggestion is to answer her sweetly, "I love you, too!" (add her name) If you can do that over and over and over and over and over again, it will make her crazy. It may actually touch some part of her on the inside that is searching for love and attention from you.
Hang in there through this hard stuff. It will pass.
<3
