Bad choice of words there. If there is one easy way to make Dairine dislike you, it's pointing out her lack of specialness. Because as far as she is concerned, she was more special once, long before she arrived her. And she didn't like reminders of her demotion.

"Oh I don't think so! Right now I wouldn't care if you were the freaking Sandman. You'll stay out if you know what's good for you."