After all, Wilson Fisk didn’t become Kingpin until the end of Daredevil’s first season, Kilgrave was never really referred to as The Purple Man on Jessica Jones, and Black Mariah was a surprise replacement for Cottonmouth on Luke Cage.
The name Alexandra makes things a bit more perplexing as there aren’t too many characters in the Marvel mythos named Alexandra — and there are even less who have any direct affiliation with The Defenders team.
Anything can happen at this point.
However, given the fact that The Defenders universe has already proven itself more than willing to play fast and loose with the origins and characterizations of particular heroes and villains, we’re not ruling out the possibility her name is a red herring to distract us from a more well-known or iconic identity.