Kory shares some traits with Bruce: great power, utter commitment, loss of family. But she also showed Dick that those qualities don't mean you have to shut yourself down emotionally.
As I recall, Marv Wolfman and/or George Pérez has said that one reason Kory is immediately attracted to Dick in The New Teen Titans is the bare legs. She can see that in some ways he's already open and not easily intimidated.
Plus, of course, there's the sex factor. They were both around twenty years old when they became an item, and the two sexiest people on the planet.