User blog comment:B214/Chapter 513: Hanamaru/@comment-4507125-20161205155546/@comment-7418318-20161206070000

Who said anything about a relationship? We are just talking about recognition here.

You can recognize people you've never talked to or even seen just from pictures or verbal discriptions alone and Kings and Queens tend to be known far and wide.

But even if as Queen she always hid from her subjects and fled before her husband/mate/whatever was killed by Acno, Acnologia should at the very least realize she is a Dragon. After all he was able to accurately count and even locate the Dragons and Dragon Slayer from half a continent away just by smell alone.