Help me cope with my siblings?

I am 13 and I have to share a room with my 5 year old sister. She is rude and ignores me and I only own a quarter of our bedroom. I didn't get to help choose the wall or carpet colours and to make it worse she gets anything she wants and I practically have nothing. I am soon to be made to use a chair bed to make more room for my sisters stuff while I only have 2 shelves in a bookcase for myself, HOW DO I MAKE THIS BEARABLE?????