She's five, its natural for five year olds to get annoying. Just take a breather and calm down. I have an older brother and sister, sometimes Onee-chan can get annoying and I get into disagreements with them, but I love both of them.
I guess it's in their nature to be annoying. I too have a little sister, but I mostly pretend she isn't there...you really should use correct grammar, it's annoying to look at.