I really like Etta!
I think it would go nicely with something else slightly unusual and a bit 'quirky/cool'. Fairly short too, I think. How about:
Astrid, Aphra, Aria, Amaya, Bronte, Bethan, Cora, Carys, Cerys, Celyn, Connie, Callie, Cleo, Dana, Delphi, Fallon, Faith, Giselle, Halle, Hebe, Heidi, Honor, Hazel, Iris, Inez, Juno, Josie, Katie, Livia, Leonie, Lyra, Mala, Mika, Mabel, Maeve, Mila, Mimi, Morgan, Noa, Niamh, Noelle, Opal, Piper, Pippa, Polly, Quinn, Romy, Remi, Rivkah, Robyn, Rowan, Sadie, Saffron, Sorrell, Sasha, Taryn, Tegan, Tamsin, Tanya, Tara, Tessa, Una, Verity, Veda, Vashti, Willa, Xanthe, Zia, Zeryn
Alban, Aston, Ario, Aldo, Aulay, Brodie, Bohdi, Colby, Caspian, Chase, Diego, Declan, Ellis, Eliah, Flynn, Fitch, Harley, Harris, Inigo, Ivan, Jesse, Jude, Julian, Jonty, Kian, Lex, Ludo, Morgan, Mason, Nico, Orson, Quinn, Rory, Rex, Solly, Seth, Sacha, Tian, Tallon, Tanner, Vinnie, West, Zeke