Clarifying the situation before I get into my question:
-I am not breaking up with her, she is the most amazing and supportive person outside being affected by BPD.
-We haven't been dating for very long(we were best friends before so we know each other very well) and this would be the first time she actually splits on me for more than a few hours.
-She has a tendency to not like when I go out by myself, and she is busy on this day so I invited her but she cannot come. I have my own friends that will be at the event so I'd still like to go. (The event is an anime convention I've been looking forward to, I would normally stay home if it was a more couple-centered event.)
-She told me herself she wants me to go, she is trying her best to not give into her patterns of being overly controlling but she can't control her emotions on the matter.
-She hates reassurance during splits and is made uncomfortable by it until a certain point of de-escalation.
-She has told me to not talk to her during the split because she could very easily accuse me of things that aren't true or try to argue.
-She does not have access to one on one therapy, she recently got a DBT textbook is learning but we don't have money for therapy at the moment so it is not an option.
With all that out of the way, what do I do? She warns me of all her splitting tendencies and tells me what not to listen to, but the advice is all about staying away and not trying to help. None of her previous partners stood up to her behavior or tried to help, and we've discovered new coping mechanisms after she says to avoid before, so maybe there's something I can do? I know she's in a lot of pain right now but I don't want her to come out thinking I hate her, which is something she's confirmed could happen. I just want to know what to do to support her without overstepping her boundaries or getting myself hurt, is the answer really to just ignore her for a few days? I know I'm not going to give up on going to this event as it's in a few days and we will likely encounter many more situations like this in the future so it's good to learn how to deal with it now. She used to be extremely controlling and abusive towards an ex of hers and neither of us want that situation to repeat, so we're trying our best to work out ways to keep our autonomy without sacrificing each other. Any help is appreciated, and you're more than welcome to share your own experiences in the replies!