Elizabeth tried her absolute best with David, and I have no doubt that she loves him, but presenting an ultimatum to him was the wrong way to deal with him. I don't think, however, that she knew any other way to go about getting David to give up on Burke.
With all the competitive talk of gifts from Burke today, I'm surprised that the crystal ball wasn't mentioned. And by the way, I find it interesting that David, the obstinate liar, admitted that Burke didn't exactly give him the picture.
Matthew came across as the salt of the earth today, giving David good, sound advice. But we've seen where his ideas about rock-solid loyalty led him: to attempting to kill Burke Devlin. The thing is, right now I think Matthew may have been right that killing Burke would make life easier for Elizabeth, if only the police (not to mention the townspeople) could be persuaded that the Collinses didn't pay Matthew to do it. I know, I know, I'm supposed to be shocked at the the thought of murder, but I just don't like Burke enough. Assuming Burke was innocent of that manslaughter, then a terrible wrong has been done him, but his suffering has done anything but ennoble him. And he has admitted he's not completely certain that he wasn't driving the fatal car. I've mentioned that I was wondering about the friendship between Roger and Burke before the accident. Everybody says that the other thing that split them apart was Laura, but right now I'm wondering if, even before the accident, when Laura was still Burke's girl, Burke liked Roger's money and status better than he liked Roger. So Matthew can kill Burke with my blessing.