Well, reading your latest post without knowing everything, here's what I think.
Your XW is going to date. D8 is going to know. You are going to hear about it. You might not like it, but those are the facts. But I think your reaction took it out on D8.
Every time you are faced with a situation like this, you need to consider, is your reaction going to make things better, or make things worse? In this case, I think you made things worse. On the one hand you might think you set a boundary. But actually it sounds to me that you just punished your D8 for things that she and you can't control. You telling her that you don't wan't a reasonable "gift" (and I hardly think a caramel apple is even a gift, it's more the polite thing to do) from your XW is not helping.
You are not detached. You let your XW's actions control your emotions. And you reacted out of anger, rather than reason.
Like I said, I might have it wrong, but that's what I read.
