Queenie's a legilimens - odds are good she could spot that there's something different about Graves, right?

So right after he's pulled the switch, she brings him his morning tea or a letter or something, and she immediately twigs there's something wrong. But he realises he's been busted and pulls his wand on her. Cue torturously hot noncon desk fucking sequence, with Queenie's french knickers round her ankles and the smooth curve of skin at the top of her stockings exposed as he bends her over Graves's desk and fucks her like a pile driver, pounding her pussy before driving into her ass as she sobs, her mind full of images of all that he's done and plans to do, until he finally cums gasping Albus's name - then obliviating her and sending her out of the room with a slap on the butt and her knickers in his pocket.

Points if this has already happened half a dozen times before, and he's already contemplating how he's going to do it next time - maybe up against the wall, or having her blow him under the desk...