Callista. I think it's younger sounding and prettier than
Estella. The Es sound of
Estella always annoys me.
Callista can also be shortened to
Callie which makes it a much more normal sounding name. Unusual names stand out and I think it is important to have the option of a name that fits in with Emilys and so on better. About
Estella, I always think
Estelle is a rather classy, elegant name. Adding the a on the end ruins it. I do however prefer the nns
Ella and
Ellie to
Callie. I'm not a fan of
Stella which might explain a bit why I don't like
Estella.
For spellings I like
Callista and
Calista the same really.
Kalysta is also pretty but I don't think it would fit so well on all age ranges.