Cersei didn’t break Dany, she was already broken. She tried her hardest to get the ppl to trust her but they didn’t, even before she destroyed KL.
She was broken when she seen how the ppl responded to Snow and when she heard the news. The people have never liked her. She freed the only people who loved and trusted her, the unsullied, plus losing her babies and Mormont.
John and her cant have a relationship, there’s that love lost too.
This is why she didn’t want the secret to be told to Sansa. Sansa knew what she was doing and if anything she’s the one who really won, she let Dany destroy Cersei and knew Dany was already going to self sabotage.
She didn’t care about trust. It didn’t matter, she never had it to begin with. So, why not say fuck it and destroy absolutely everything? She’s just going to use the Cersei tactic, she sees how stupid people are, another reason she didn’t care. She can rule w an iron fist now.
Arya has a different outlook, though.