You and DP really need to work on the idea that you never speak about anything until you've spoken in private.
This is the catalyst for this conversation. Express your disappointment. Tell her a little piece of you died.
BOTH of you should make that promise.
and you also should feel free to interrupt her and say, "Oh, DP, we need to check on some things before we offer that." Which gives you something you can do when you're there.
But you can't always be there, so that's why you need the rule.
All couples need that rule.
And I agree w/ NyaChan--call and say, "We spoke too soon, we're so sorry." The faster you act, the less damage to them. And absolutely blame her health. Maybe even blame the dog--honestly if he's trying to protect you from these strangers, he can't be as effective at his service-dog tasks.
And cicero is right--the memories (and the resentment) will be longer than if you contact them and say, "we spoke too soon."
If DP won't do it, you should.