I never thought about pronouncing it "fee-dell-ees." That's very pretty. Have you actually heard it pronounced like that? I'd be interested to know.
I've been thinking of it more like "fi-DEL-iss" or "fi-DAY-lis."
Would you be more interested in
Fidelia? (Which I assume is "fi-DEH-lia" or "fi-DAY-lia.")