He made a joke.
She took it personally.
She said a sarcastic remark.
He wondered what she meant by it.
He mentioned a past interaction, simply because the memory popped into his mind.
She thought about the past.
He changed the topic.
She snapped at him.
He stumbled, shocked by the impact of the sting.
She misinterpreted his silence and was sucked into the quicksand of her own doubt.
She launched a full-out attack at his perceived assault, in defense of her own shortcomings.
He shut down.
She continued her tirade.
He made an excuse, said he had to go.
She started to cry.
He said he was sorry, then added that he didn’t know what for.
She hung up.