The only difference between Aphrodite and Leah (and one of the few comforts we get) is that one of the two authors does like her. PC Cast has stated that Aphrodite is her favorite character, which probably explains why she becomes more prominent and gets a bit more development. Unfortunately, she parallels Rosalie in that from what I gather, when she is given more development, she starts to turn into a sycophant for Zoey.