I quite like Violet and Scarlett. Do you like colour names in general?
If so, how about:
Ruby, Cherry, Jade, Emerald, Sapphire, Bianca, Ebony, Rosa, Rose, Sienna, Clementine, Indigo, Amber, Hazel, Jasmine
Otherwise, I think these have a similar vibe to Violet and Scarlett:
Alexis, Alexa, Alyssa, Alicia, Ariel, April, Aurelia, Antonia, Astrid, Annabel, Annette, Asia, Aurora, Bethan, Bonnie, Catriona, Claire, Claudia, Cecilia, Clara, Cynthia, Cecily, Clarissa, Cassandra, Constance, Daphne, Eloise, Erica, Erin, Esther, Georgina, Giselle, Hermione, Harmony, Iris, Joanna, Juliette, Josephine, Kaitlyn, Lillian, Lucinda, Lydia, Louisa, Larissa, Leonie, Madeleine, Melissa, Miranda, Mila, Nicole, Natasha, Nadia, Ophelia, Penelope, Rhiannon, Rowena, Romilly, Saffron, Savannah, Sorrell, Saskia, Summer, Serena, Sabrina, Tamsin, Tessa, Tabitha, Verity, Vanessa, Willow, Xanthe, Yasmin