Quote from : The Blood of Olympus Book

Percy pulled Annabeth close and kissed her...long enough for it to get really awkward for Piper, though she said nothing. She thought about the old rule of Aphrodite's cabin: that to be recognized as a daughter of the love goddess, you had to break someone's heart. Piper had long ago decided to change that rule. Percy and Annabeth were a perfect example of why. You should have to make someone`s heart whole; that was a much better test.