You have to watermark "everything" these days.. If you do not (with it being digital media), honestly, you have to think about it this way: she was dumb and blatant,how many people do you think honestly have not gotten caught using your media? And even, with a watermark, someone that is good in photoshop, if they really wanted (though, for coral pics, I doubt anyone would go to such extremes, but you never know) to, they could remove it..
But a huge way to cover yourself is the watermark.. And to be crafty with it.. Ie:not just one big watermark, but placing tiny ones in areas that no one would notice. That way, if need be, and legaity(DR intellectual disputes) came into play, only you, the content creator and owner will know exactly where it is at..
But short of that, a water mark that had to be cropped crazily will deter the average digital sticky finger...