Should I tell my 7 year old sister to fuck off in front of my entire family?
It seems a bit extreme. Are you going to be vulgur because you find her annoying?
Yes, I want to tell her to fuck off, because she always insults me when I'm sitting next to her, what kind of sis is she?!
You shouldn't be vulgar to your sister. Your family will resent you and she will be justified for her actions.
I'm not worried since they always ignore me anyways.
Your sister is only 7 and children are expected to be annoying and do stupid things. Telling your sister to fuck off is way too much of an adult expression. Why not just tell your parents that your sister is annoying you again and have them reprimand her?