What if Tina had been suspecting something was wrong with Graves the whole time, because they had previously always been engaging in flirtatious banter? Maybe even to the extent the rest of the office had a will they/won't they pool of bets on if they'd ever get together. Of course when Grindelwald takes over, he resoundingly shuts Tina down, and this is essentially the only Graves trait to change so everyone else just figures he moved on. Then the events of the movie happen, Tina rescues Graves like a badass, and happy ending!