I've ran into Derpy a few more times since then; thankfully, no incidents that she needed help from. Sometimes I catch her dropping mail off at my house; sometimes, I get home and find them neatly sorted on the table. She's getting pretty good at landing through my window without making a mess. Now and then I'll bump into her on the street, and we'll pause for a bit, chatting. Tried to invite her for a coffee, but she just doesn't have the time. She does get Sundays off, though... might ask her about that.