I've read Omerta, and I don't recall it ever mentioning Graziella as the Corleone don? If I'm wrong, please help me and point out where it says this, It would be greatly appreciated, thanks!
He wasn't. He was said to be the Corleonesi Don, which implies that he was the local Don in Corleone, Sicily, as the people there call themselves the
Corleonesi. There was absolutely no mention of the Corleone family in the novel OMERTA.