I think Callista has two "Ls" no? It fits the bill to me.
I love Anthea, but I hear Americans pronouncing it ann-THEE-yah, rather than Ann-TAY-ah, which I believe is the correct pronunciation, as in Parmigianino's famous painting Portrait of a Young Girl Named Anthea. I like it, but only with that way of saying it.
Violet, Anthea, Calista, and Camilla fit that description to me. Violet's becoming trendy, and it's more popular than the others, but it's still refreshing enough and uncommon enough that it feels very fresh to me. I'd love to meet a little girl with any of those names!
I feel like Clio and Freya should fit that, too--I admit, I just don't like them very much. :( Nice names, just not for me.
Calista - Fits, but a little less common but easy to say and spell.
Clio - is it pn Cleo? I like it though.
Camilla - Fits the sweet spot
Freya -Love Freya!
Violet - Very popular right now and moving up I think.
Anthea - Love it - but I do pn it Ann-THEE-a is that right?
Christabel - This is obscure but easily said