NTA
I feel like the only thing that might be even remotely be a mark against you is if it really was as quick turn as your post makes it seem. Even if it was a deserved ultimatum - if you allow them the option to break the news themselves, I think an allowance of a day or two to form the right way to break it to them might have been better for her current standing with the kids.
But ultimately - no matter how much time you gave her to prep that speech, it likely wouldn’t have saved enough face for them to feel more cordial in the short term.
Yeah, there were a few headlines where I was like “Well… maybe? If I can’t actually read it I’ll assume false, though.”