Depends, if she's a older sister, like me, then yeah, us older sisters can be protective. I am of my baby sister, she's my only sister, and we're close. I might as well be her second mother. Us sisters like to look out for one another, and when we see the other is down, we will find out whats wrong, and then try to cheer you up. If your the oldest, then your younger sister is probably tryingto be like her older sister by bugging you and seeing your reaction so she can act just like that.
Tell her calmly that you just wanna be left alone and she might leave you, if not just be really straight and tell her exactly how you feel .. hope this helps :)
She's probably just looking out for you, like all sisters do. Just be honest with her and tell her that you don't like when she's on your back all the time.
depends why she is on your back. i usually just pinch my sister so she will kick my ars then il cry a while...yh not the best idea.
it depends on how old she is if shes younger she wants her sister around if she older shes looking after yuh
throw her off of your back, but if she is bigger than you, flop on your back and crush her she will let go
lay on her! and dont get up! trust me it works and its fun :D
xD . D: Im like 5'8 tall and shes 5'2 with a temper