Continuity mistake: While Hippolyta is dying her hands move on Diana's body between shots.
Continuity mistake: While Hippolyta is dying, there is a sword on a bow which disappears between shots.
Continuity mistake: When Steve and Diana get to London, he is on her left then on her right.
Continuity mistake: At the bar while the bald guy is pointing with the gun, Diana is across the table, but in the next second she is beside the gunner.
Continuity mistake: At the beginning while Diana as a child is running among the people, a girl in gray is walking differently between shots.
Continuity mistake: After Diana crashes through the window, there are various bits of wooden debris on the floor in front of her. In a wider angle those bits have vanished.
Answer: It would be more accurate to say they grow to a certain age then stop aging. Similar to the elves in Tolkien's Lord of the Rings.
jimba