I really like Francesca. Not keen on Nancy.
I know Imogens with sisters called Natasha, Madeleine and Laura.
Other ideas:
Alexis, Alexandra, Amber, Abigail, Charlotte, Caitlyn, Erin, Florence, Georgina, Hannah, Harriet, Jessica, Joanna, Jasmine, Kathryn, Miranda, Matilda, Melissa, Miriam, Olivia, Philippa, Rebecca, Rhiannon, Rachel, Saffron, Tabitha, Tamsin, Victoria, Vanessa, Violet, Yasmin, Zara.