[NadiasWilly]

By convincing him that Charlie had it won and desperately needed the money.

Think about it, there's no way she would have wanted him to stay in that house without her. They all hated her so she would be paranoid about them turning him against her. The thought of him getting close to siavash and Marcus and all three of them comparing notes about her. The things they could have told him about how she behaved.

Then there's the female threat. In her aftershow interview Noirin implied that Bea fancied Isaac. No way would she leave him in there for Bea to get her claws into!

Isaac is a hardcore gameplayer. Noirin knows he would do anything to win. Including flirt with HMs. She also knows that the only way he would quit is if he knew he could not win the prize.

So she convinced him that Charlie HAD TO WIN. Then there would be nothing to keep him there. Just a house full of strangers who don't like him.

So he quit. Because of Noirins jealousy. Kinda ironic.