Oh, I like Carolyn much better, or Caralie, or Coraline, or something. Carys will be difficult to pronounce and might get her teased. Or you could use something else for her first name, and make Carol the middle name.
Some other suggestions, for middle or first to go with it:
Anastasia, Aislinn, Cecilia, Natalya, Emilie, Lillian, Vivian, Alcyone, Aramina, Annice, Skylar, Jessabelle, Calliope, Lessa, Mercedes, Dierdre, Rosalind, Abigail, Eleanor, Lilith, Anya, Fiona, Guinevere, Genevieve, Delia, Delilah, Lilith, Cordelia, Lorelei, Evelyn, Anneliese, Quinn, Rowan, Lyta, Lilyana, Erin, Brianna, Vaneris