User blog comment:IamJakuhoRaikoben/Chapter 454: Flying Dragon Squad and Osprey Squad, Review./@comment-177.107.9.105-20151003000826/@comment-7418318-20151003071635

Levy said that Nakagami wasn't used in decades, not that it was used a decade ago.

Bisdes for Levy at that point "a decade ago" would likely mean 17 years ago due to timeskip and another year due to the 2nd timeskip. Does Dimaria look old enough for you that she could have used Nakagami 18 years ago, when she was probably around 4 to 7 years old by my estimate?