The Norberta reveal actually happens in Deathly Hallows.
No wonder I don’t remember. That book was a fat blur.
And frankly, I don‘t see a shift that is connected to the movies.
I saw it more in Book 4 and 5, when her writing style changed from something akin to Roald Dahl into a more Twilight/Hunger Games esque YA dramady. She was in the middle of writing Book 4 when the first film premiered and ended up selling the rights to the movies before the fifth was officially started.
The size the books swelled, and you could tell there was a lot more editorial/ghost-writer punch ups happening along the way. What started as these cute little Christmas-y children’s stories mutated into enormous screenplays.
What I actually observed was the overcompensation for criticism two books after the fact
Once Rowling got on social media and started yapping her yap, I think it cast a shadow on the series. The stuff about goblin bankers being a stand-in for jews and the sloppy way she fumbled through Hermonie’s SPEW plotline took on an increasingly sinister cast as she got more vocal in the wake of her movie debuts.
Also not unlike Roald Dahl, the media comments forced people to re-contextualize a bunch of these fantasy tropes as legit derogatory views.
Whether they were there early on or whether they only really found their legs once Rowling started hanging out with a bunch of rich British freaks… idk. But they definitely became more obvious as she climbed the economic ladder.