I hate being a sibling

Why do siblings always know exactly where to peirce you with a knife to make it hurt so bad that you just want to crumble into a million pieces and just break down and fall and cry forever. They can always make sure you are always either happy or sad. One jab of that stupid knife of theirs and youre down for the count.
I hate feeling left out and hate when people make me feel small and my sisters know that. I just went into my sisters room real quick to tell her something and she told me to get out. (not a good thing to do). i felt so small. I wanted to cry which is what im doing now. I told her its not nice to be rude. and she said well you keep hanging out with me and amber(her friend who is over). i said no i dont which i dont. and she said its not my fault you are a loner. (the worst thing you can say to me because i only have one friend).
it hurts so much. she is the one that will make me start cutting again.
anyone in this situation??