JYP was really taken with Ayaka as soon as he saw her because she reminds him of Suzy Bae from Miss A. He was hoping she has the same talent which, as you'll see later, she does.
Nina was too young to understand the song, at least I hope no 14 year old understands the emotions in that song. Her voice is great, but the way she sang that song made me uncomfortable. If you're curious you can watch the original https://www.youtube.com/watch?v=nfs8NYg7yQM