When someone who doesn't know any better on line calls me a "gurl", I just have to set them straight. I have always thought a "gurl" was a gender slur not unlike the "T" word or tranny. Or, at the least it ties me in with someone like a fetish cross dresser or even "she male". For the most part though, most are very understanding when I tell them my reasons for disliking the term.
In my regular life I'm fortunate. My close little circle of friends just call me Cyrsti, she or dummy and life is good. In the chance though that someone does call you or I a "Tranny", I'm passing along one person's idea of how to handle it on the Cyrsti's Condo big screen: