Do you think it's bad that I despise my sister for being skinnier than me?
Does your sister being skinnier than you have any effect on your life?
No, but that bitch is skinnier than me.
It doesn't make sense why you would hate your sister for being skinnier than you. If you are jealous of her you should try to work on yourself, because hating her doesn't really help you.
She's super annoying, though.
I know it can be hard to be jealous of a sibling, but it doesn't get you anywhere to hate her for being thin. Jealousy isn't productive, it's destructive.