The scene in BvS where Diana says this line to Bruce is so interesting. Because at that point, he's totally in Bruce Wayne billionaire playboy facade. And he thinks he has her figured out in the same way he has Selina figured out. He thinks that Diana is out for a profit, or she is out to toy with him in a game of cat and mouse or something.
And then she just gives him back that flashdrive, which throws him. Diana was actually motivated by her love for Steve and wanting to get that photograph back, which is totally not what Bruce was expecting. She threw him off his game completely; so much for the greatest detective
