My favourites are Grace and Ada.
Other ideas:
Ava, Astrid, Aphra, Amy, Ayla, Anya, Agnes, Amber, April, Ariel, Asia, Asha, Adele, Bronte, Briar, Bethan, Clara, Carys, Cerys, Callie, Cassia, Celeste, Dana, Darcey, Daisy, Dora, Erica, Eva, Efa, Ella, Ellen, Esther, Effie, Enya, Etta, Erin, Eden, Flora, Farrah, Fallon, Ffion, Freya, Faith, Hallie, Hope, Holly, Hazel, Heidi, Isla, Iris, India, Ingrid, Jasmine, Julia, Joelle, Katie, Kayla, Keira, Livia, Lyla, Lyra, Lara, Laura, Laurel, Lauren, Leah, Lois, Layla, Lacey, Mila, Mala, Mika, Morgan, Molly, Maisy, Mara, Mina, Nicole, Nia, Nyah, Niamh, Nora, Noa, Noelle, Orla, Opal, Olive, Paige, Quinn, Ruby, Rhiann, Rachel, Sara, Sophie, Sadie, Shannon, Summer, Skye, Thea, Tara, Tansy, Taryn, Una, Willow, Xanthe, Yasmin, Zoe, Zara, Zia