Not really, not at a birthday party... even vanillas often do this. One of the reasons I love going to birthday parties.
Not if the Dom spent weeks teasing his sub about getting spanked ahead of time.
And he was no doubt prepared to monitor the proceedings to make sure any paddler didn't go overboard.
I think that the invitation should have included a "Kinky Agenda" but... lacking that, a spanking/paddling of a submissive birthday girl is to be expected.
I think the advice, in general, is good.
A simple refusal, "no thank-you" would have sufficed.
A future, semi-contrite, explanation of what happened will salve any concern of the other attendees (and by semi-contrite, not that chalsia need say she was wrong for refusing, just enough contrition at her own over-reaction, no more or less than she showed in her post.)