I find that I'm really, really put off by the spelling. I can see that Celia Casella could be slightly odd at first, but it's not bad - and not silly either, like John Johnson. And since Cecilia and Cecelia sound the same, you could still use Celie if she was a Cecilia.
If it was me, I'd use Cecily in a heartbeat. But of course it isn't me!