Welcome and pull up a chair
Weddings and BPD. There should be a whole section just for family gatherings and personality disorders.
Congratulations on setting a boundary. $1000 for a hotel room is just, wow. Great that you could let her deal with the consequences of the group rate problem. That's her bed, for her to make.
My first move would be to set Venmo to private so she can't snoop on you there.
This is a small tip but I find BPD projection is so primitive that you can pretty much swap out pronouns and it's them talking about themselves. "I'm so selfish, I don't care about family." Because expecting family to pay that kind of money plus flights and whatnot is not exactly thinking of you.
As for scenario 1, how do you feel about checking in with people to check your hypothesis. "Are we good?" That at least gives you an opportunity to find out if your fears are founded. I know people recommend to not care about these things and take the high road. That's also really hard to do.
Scenario 2 is something I worry about with my sibling (uBPD). He likes to humiliate me in groups, preferably during a lull in conversation. He has an uncanny ability to make it seem like a joke, so if I don't lighten up I come across as overly serious.
The bigger issue is that these are probably things that are painful for you for some reason, and so carry emotional weight. Either your sister says many mean things and these are the ones that are particularly painful, or she knows these are painful and goes for the jugular.
Depending on which one it is, you have different options.
I wish I could say I've been successful over the years at learning how to handle these moments. Sometimes the best I can do is get myself to safety. Often I'm overcome with physical issues that make it hard to rise to the occasion, or shrug things off. I was watching a female politician being public humiliated by our former president in a way that was similar to what my sibling does, and the female politician simply said, "Please do not mischaracterize my achievements." It struck me because she kind of neutralized things without getting into a pissing match.
I try to go for those types of responses. "Please don't mischaracterize me."
As for how you look, would a shrug work? For BPD people in my life, I try to not show much emotion otherwise it gives them ammunition.
Or changing the topic. "It's your day. Let's talk about how lovely you look." (I mean, I wouldn't be able to do that, but it's a strategy).
When it comes to things you said about your husband, I would get ahead of that and tell your husband. I've had to do that with my current H. My brother likes to drag things out of the closet I would like hidden. There is nothing my sibling can say about me my H has not already heard, and we've been able to discuss the context from my point of view.
Is he in your corner? I would also ask him to help you throughout the event. My H stays by my side as much as possible, and he also helps me when I regress. My sibling likes to whip up anxiety and discuss negative things. He thinks and talks fast and I end up on my heels. H watches for these interactions and kind of pulls my shirt to remind me to talk a walk or get some air.
