Wow. Well first as to comeback to the EII's rude statement to you, when you realize someone has hurt you with their words and you haven't have time to process just what it is they said and why it hurt, you can always come back with "What?", asked without irritation but kind of mild blank curiosity that shows you sincerely wonder why anyone would ever say such an odd thing. They can repeat it (getting to hear their own rude selves again, a chance to second guess how that might have sounded to hear) and if you are still not satified (or they aren't uncomfortable yet) you can then say, "Why would you say that?". They respond, and you can still look at them silently for a moment, ending it with, "That is an odd thing to say." or "That is rude" (or "unkind"). And in this you are not acting badly as she was, because you are not saying her "You are..."; you are instead saying to her, "That is...", thereby addressing what she said, not her entire character, which is more appropriate and just.
It works every time.
Also I wanted to say I really liked your open and honest explanation of your reaction to that social setting. I know ESE's who talk just like that! Although I do not have that reaction you had, and I enjoy what ESE says. But, after a long conversation with ESE and after we part I realize they never asked about me of my interests, and I never had a chance to express anything of importance to me. It was always all about me listening to them. Which I like to do, however, I find with ESE its pretty consistently one-sided. I guess that's what to expect from Benefactor relations. I should know, I was married to one.
Your detail of your reaction to the conversation is informative to me, and makes me think that at times when I might be happily sharing about something of great feeling-value to me, I should "check" reactions of the other person: are they polite or sincere? And if possibly just polite I should tone it down, or pause a goodlong time to give them the opportunity to change the subject if they wish, or, if they did like what I was saying, they can ask me to continue, or ask me more about it, and only then will I go on. If they change the subject then I know they weren't into it.
This is like the important principle in teaching "Check for Understanding". In conversation, I guess the rule would be "Check for Interest"! ..