It makes no sense for Richard to come near suicide over Margaret, when the two have never before interacted. Neither does it make sense for Andrew to elope with Margaret. But wait! Remember all the way back to Chapter 4? (or Chapter 17, depending on your preference?) Andrew specifically asks Richard about Margaret Eastman. Richard claims to not know her, but Andrew thinks about how he has all sorts of pictures of her... so it kind of makes sense in the end. Or at least there's a vague, tenuous connection there.