Gail has presented Etta and Diana as though they were super-tight bosom buddies who've been aw shucks besties 4 life! for years. This take on their relationship has precisely zero foundation, and no emotional resonance, because the last twenty years of canon has demonstrated quite clearly that there are easily hundreds of people with whom Diana is closer than she has ever been or probably could ever be with Etta.
But wasn't that shortly after the Crisis? Canon wasn't the same after that, in the new canon isn't it possible that Etta and Diana really have been BFF?