How to be flirty in a friendly way?

Hmm how about not .. lol ... j/k why don't u just treat her like a sister .. I don't see why u have to think about actually flirting with her ... do u have a sister? well, I'd just be myself and not let get borderline ..=D.. stay away from the alcohol .. cousins are notorious when it comes to having ual encounters happen = / it's happen way too much in history.