I'm not a fan of Katherine and I think Ella is really really pretty. I guess it depends on how formal of a name you want. I personally think Ella is great on it's own but I know a lot of people on here would think it needs a more "formal" name with Ella as a nick name.
Re: Girl Name
I like Ella much better
I like Katherine Ann better than Ella Ann. With Ella Ann I think the two "a" sounds run together. I prefer the spelling Catherine though.
What about:
Elizabeth Ann (you could call her Ella as a nickname but then when she said her full name the first and middle names won't run together)
Evelyn Ann
Jillian Ann
Caroline Ann
Corrine Ann
Emily Ann