Okay, so I guess you need to forget the popularity criteria and go for a name that is safe but classic?
Ummm ....
Amy, Alexandra, Aurora, Bryony, Beatrice, Caroline, Christina, Claire, Daniella, Erica, Erin, Francesca, Georgina, Harriet, Hannah, Isabel, Imogen, Jessica, Joanna, Jennifer, Julia, Katherine, Katie, Lily, Lucy, Lydia, Maria, Mary, Madeleine, Miranda, Melissa, Matilda, Nicole, Nicola, Natalie, Natasha, Olivia, Philippa, Phoebe, Rebecca, Rachel, Sarah, Sophie, Sophia, Stephanie, Tabitha, Victoria, Vanessa, Verity, Zoe.