that incident I mentioned before

We were sitting on the grass after a rounders match and Miss Lucy had been giving us a typical talk on smoking when Marge suddenly asked if Miss Lucy had herself ever had a cigarette. Miss Lucy went quiet for a few seconds. Then she said: "I'd like to be able to say no. But to be honest, I did smoke for a little while. For about two years, when I was younger."
You can imagine what a shock this was. Before Miss Lucy's reply, we'd all been glaring at Marge, really furious she'd asked such a rude question--to us, she might as well have asked if Miss Lucy had ever attacked anyone with an axe. And for days afterwards I remember how we made Marge's life an utter misery; in fact, that incident I mentioned before, the night we held Marge's face to the dorm window to make her look at the woods, that was all part of what came afterwards. But at the time, the moment Miss Lucy said what she did, we were too confused to think any more about Marge. I think we all just stared at Miss Lucy in horror, waiting for what she'd say next.
When she did speak, Miss Lucy seemed to be weighing up each word carefully. "It's not good that I smoked. It wasn't good for me so I stopped it. But what you must understand is that for you, all of you, it's much, much worse to smoke than it ever was for me."
Then she paused and went quiet. Someone said later she'd gone off into a daydream, but I was pretty sure, as was Ruth, that she was thinking hard about what to say next. Finally she said: "You've been told about it. You're students. You're... special. So keeping yourselves well, keeping yourselves very healthy inside, that's much more important for each of you than it is for