I have never heard of Agnelia but I think it is nice variant of
Agnes. Another one is
Agnessa.
Annis is yet another variant.
If I loved Agnelia, I would use it, made-up or not. It sounds like a "real name" and the family association makes it "legitimate" enough imo.
"You may give them your love but not your thoughts. For they have their own thoughts.
You may house their bodies but not their souls,
For their souls dwell in the house of tomorrow, which you cannot visit, not even in your dreams."
(On Children by Kahlil Gibran)