Daisy didn't know why she did it - why did she even bother approaching him? It may have been her incessant belief in people. It may have been her boredom. It may have been her rare but definite character trait known as stubbornness. Maybe it was that she wanted to like Barty, to give him a second (or third or twelfth) chance at being a good person. Even worse yet, though, it may have been the fact that she had no reason. And this was what worried her. Perhaps she was as daft as he treated her...
Without greeting him back and with the most stern face she could muster (it consisted of knitted brows and a small pursing of her lips, but that was about it), Daisy looked him up and down with her blue eyes nearly red with fury, or as much fury as the small girl could hold. Daisy had nothing against smoking, but the fact that Barty was doing it so confidently made her feel as if she did have something against it. Of all of the girl's incessant needs (to believe in people, to please, to be liked), one of her less humble ones was her incessant need to respond to people. She always had a hard time ignoring people. Why? Most likely because her brothers had a knack for not hearing a word she said and making fun of any of the words they did care to catch. This may also tie into her need to almost always have the last word. However, she pulled herself together momentarily enough to ignore his comment and move on to his next.
Daisy could feel her nose wrinkle at every move Barty made and her body was nearly on complete defense mode whenever he opened his mouth. "Working on being an arse, I see," she shuffled her feet around a bit, she felt a bit funny standing so high above him in her skirt, "Good job, really. I'm really buying it. I think you've got it down pat."