Owls cared little about names. They relied on their master's concept of the recipient in some faint sort of telepathy. This ability was unique to owls, explaining why one would only occasionally see messengers belonging to any other species. Those countries without an indigenous owl population used other methods, but none of these have the ability to deliver without needing an address or a real name. Assuming Albus would use an owl to communicate with her, the fact that she'd given him an alias wouldn't matter.