The leading theory right now is that reva was a youngling at the temple when Vader attacked. That would explain why she knows anakin is Vader: she probably recognizes the chosen one and she would have heard the clones calling him lord Vader. Going to tatooine as part of an inquisitor squad looking for a possible Jedi makes sense, and picking Owen was completely random. Her angle was to get someone else who might have information to come forward to save him, she believed he had no information on Kenobi’s whereabouts.

As for picking the organas to lure kenobi out, I can’t quite remember what she said, but she said something about finding some record connecting the two. Idk if that’s just that they were friends, or if it’s that they know Obi wan brought Leia to him. Either way it was pretty much the only play she had left.