What does Catherine say to Isabella in the hopes that she will turn away from Heathcliff?

One example of a warning that Cathy issues to Isabella is as follows;

“I wouldn’t be you for a kingdom, then!” Catherine declared, emphatically: and she seemed to speak sincerely. “Nelly, help me to convince her of her madness. Tell her what Heathcliff is: an unreclaimed creature, without refinement, without cultivation; an arid wilderness of furze and whinstone. I’d as soon put that little canary into the park on a winter’s day, as recommend you to bestow your heart on him! It is deplorable ignorance of his character, child, and nothing else, which makes that dream enter your head. Pray, don’t imagine that he conceals depths of benevolence and affection beneath a stern exterior! He’s not a rough diamond—a pearl-containing oyster of a rustic: he’s a fierce, pitiless, wolfish man. I never say to him, ‘Let this or that enemy alone, because it would be ungenerous or cruel to harm them;’ I say, ‘Let them alone, because I should hate them to be wronged:’ and he’d crush you like a sparrow’s egg, Isabella, if he found you a troublesome charge. I know he couldn’t love a Linton; and yet he’d be quite capable of marrying your fortune and expectations: avarice is growing with him a besetting sin. There’s my picture: and I’m his friend—so much so, that had he thought seriously to catch you, I should, perhaps, have held my tongue, and let you fall into his trap.”