What do you think about me telling my sister to fuck off?
Why would you want to tell your sister that?
My sister is very nosy. I want her out of my life.
You shouldn't use that kind of language with your sister. Just tell her how you feel and I am sure she will see your point of view.
She will get mad and cry. I don't care anymore. I just want to tell her off.
Cursing at your sister will only damage your relationship. It's best to wait until you've had time to think about your problems with her before you address her.