harry potter - How did Hermione catch Rita Skeeter?

At the end of Goblet of Fire on the train back to Kings Cross the trio are sitting in the compartment when Hermione tells Harry and Ron about Rita being an unregistered animagus. She then shows them the jar with the beetle in it. I am curious to know how Hermione managed this.

I doubt that Rita willingly transformed into an animagus at Hermione's polite request, even if threatened with being exposed as an unregistered animagus.

My thoughts are that Hermione would have had to find her somewhere in the grounds already as an animagus and catch her, but then how does she have the conversation she alludes to when telling Harry and Ron about it on the train? It would have to be a two way conversation I should think, so how could Rita respond if she was a beetle?

I doubt there is anything in canon, but does anyone have a different theory?

Answer

'You're kidding,' said Ron. 'You haven't – she's not–'

'Oh, yes she is,' said Hermione happily, brandishing the jar at them.

Inside were a few twigs and leaves, and one large, fat beetle.

'That's never – you're kidding –' Ron whispered, lifting the jar to his eyes.

'No, I'm not,' said Hermione, beaming. 'I caught her on the window-sill in the hospital wing. Look very closely, and you'll notice the markings around her antennae are exactly like those foul glasses she wears.' - GoF, Chapter 37

... and THIS is the moment when it happened (right after Dumbledore had an argument with Fudge, and then sent Severus Snape and Sirius on their errands in the end of Chapter 36):

'It wasn't your fault, Harry,' Mrs Weasley whispered.

'I told him to take the Cup with me,' said Harry.

Now the burning feeling was in his throat, too. He wished Ron would look away.
Mrs Weasley set the potion down on the bedside cabinet, bent down, and put her arms around Harry. He had no memory of ever being hugged like this, as though by a mother. The full weight of everything he had seen that night seemed to fall in upon him as Mrs Weasley held him to her. His mother's face, his father's voice, the sight of Cedric, dead on the ground, all started spinning in his head until he could hardly bear it, until he was screwing up his face against the howl of misery fighting to get out of him.

There was a loud slamming noise, and Mrs Weasley and Harry broke apart. Hermione was standing by the window. She was holding something tight in her hand.

'Sorry' she whispered.

'Your potion, Harry,' said Mrs Weasley quickly, wiping her eyes on the back of her hand.