Most of them like Taylor Swift, I think, including Nia, Kendall and Maddie.
Maddie has said she likes Sam Smith. I'd assume she likes Sia, too...
IIRC, Mackenzie is a Meghan Trainor fan.
IIRC, JoJo is a big fan of Miley Cyrus, especially because Miley was nice and paid attention to her at a concert a long time ago (or something like that.)