Hi Minga7270 and a warm welcome

Sounds like you've ridden the BPD rollercoaster enough to be asking this question:
Our dilemma: Our daughter is very good at telling half truths which would lead us to draw the wrong conclusion. Are we only getting partial truths, now? Is this situation as bad as she portrays it?
Many pwBPD feel most comfortable in a "victim" role or posture, where "things just happen to them", it's not their fault, they're not to blame, life is hardest on them, and so on. As pwBPD struggle to have real sense of being a self, many use external events to prop up their personhood -- if bad medical things happen to them, they are truly a victim (finally, an identity to have) and are to be given attention, support, care, etc.
Absent those kinds of things happening in their lives, they may, out of harmfully intense emotions that demand that they feel like a self, do whatever it takes to generate external events that confirm to them "yes, this is who I am -- a blameless victim of circumstances". And those external events may be generated verbally, from a grain of truth. The doctor took her blood pressure = "he thought I have the most dangerously high BP he's ever seen". The doctor did a routine blood draw = "she hinted that it could be cancer".
It would not surprise me to hear that a pwBPD would take routine medical comments and use any grain of truth to construct an extreme situation that funnels concern and attention towards her. Whether that's the case for your D or not, we don't know, and, like you said, because you have no access to her medical records, we likely won't know.
In fact, it may be helpful to steer energy away from "figuring out what is really going on" -- which is not very possible under these circumstances -- and towards "what do we really have control over". It must feel agonizing to know that an innocent child's life seems to be in the middle of all this chaos, and there is little you can do to protect the baby as it hasn't been born yet.
pwBPD often make high-risk choices about their lives. It is so hard to watch that happen. We don't have direct control over those high-risk choices, typically. We can control what we participate in, though.
It sounds like you are not hosting the shower -- that it's all something she put together?
It's a weird question, but do you want to go to the shower?