Honestly, I'm surprised this trope still gets so much traction. The whole 'order discovers Harry's dating Daphne Greengrass' setup works because it layers so many built-in conflicts. You've got the obvious blood purity tension, of course, but the juiciest secrets often aren't about her family's politics at all. I've read versions where Daphne’s an unregistered Occlumens hiding her sister’s prophetic nightmares from everyone, including her own parents. The Order freaks out because they think she's a spy, but the real secret is that she's been using those skills to passively shield Harry from Voldemort's mood swings for months.
Another angle I liked was Daphne quietly funding the Order through the Greengrass family's international banking contacts, which are completely separate from the traditional British pureblood networks Dumbledore knows about. The secret isn't malice; it's that she's more politically and financially connected than anyone guessed, and she’s kept it quiet because showing her hand would ruin the advantage. The fallout is less about outrage and more about the Order realizing their intelligence is embarrassingly incomplete.
My favorite twist, though, was a story where the 'secret' was that Daphne already knew about the Horcruxes. Not through dark means, but because she’d been piecing together clues from old family archives about magical objects that could fracture a soul. She’d been trying to find a way to tell Harry without sounding insane, and the Order’s confrontation forced it all out. The dynamic shift—from them interrogating her to her essentially presenting a research report—was fantastic.