"I expect though that its only that if its returned. And clearly, since I'm all kinds of terrible and since you're so desperately in love with Tyler Lockwood there's no chance of that, so you tell me its not a weakness. You keep your sunshine and rainbows and 'good'. I'm going to keep thinking its a weakness until I'm proved wrong." Her ideas were all well and good but she never did take into consideration that circumstances in this case didn't lend themselves to happy things.
And of course like her, sometimes Klaus didn't know when to stop. When he'd said enough. Perhaps it was what drew them to each other. "Though perhaps, drawn as you are to me, to what I'm capable of, maybe you're not as desperately in love with Tyler as you like to think you are. You'd think one so in love, that would be enough for them. I think perhaps the lady doth protest too much."
Maybe he wouldn't let it get to that point, but what did that mean, killing her, compelling her to forget him? Neither was a particularly agreeable plan in his eyes. And then of course there were the friends, the little circle of them, telling her she was right to despise him, that she could never possibly fall for him.
He just thought perhaps on some level, she already had.