I think a nerdy, small chested girl who thinks she is better than you from all her reading and stuffing her brain, needs to have all that intelligence stripped out. Not lobotomized, just all her smarts and learning removed. Either scooped out slowly, tormenting her for hours/days as everything she learned fades away as those neurons are removed and piled on a tray. Alternatively you could just fry those neurons.
I think it's a better story than him getting fed up with her and putting both hands on her head. She feels a bolt of lightning in her head and her world closes in. All of her knowledge and intelligence fries in an instant. But otherwise unchanged. She could go start reading and get it back, but she lost how to read...
if you brain fuck her then, she wouldn't notice as most of the brain your fucking was already dead. But the change is abrupt when your dick hits what's left of her conciseness. Too stupid to say no before it was too late.