I personally think the strongest point you can make is that it's been proven that EVEN IF you smoke in the same room as her brother, the second-hand smoke hysteria is ALL BUNK. It's been disproven. You pose no health risk to anybody by second-hand smoke unless they have an allergic skin reaction, or you kidnap them, handcuff them, and force them to hotbox with you. I saw an interview w/ the guy who originally wrote the "scientific" papers on second-hand smoke, the guy who started all the hysteria, and he confessed he faked the report and was pressured into doing it. And subsequent studies have shown that even the effects of long-term second-hand smoke exposure are so arbitrary that they could even been good for you.