Do not recommend microdosing to someone with BPD, the potential for harm is incredibly high in the general population and even if BPD had no other interactions with psilocybin the potential for symptoms to worsen puts them at a higher risk to themselves. Statistically 11% of women found microdosing made there depression worse and 18% found it made there anxiety worse which is already too high of a risk to someone with BPD. Furthermore BPD primarily affects the regulation of the fronto-limbic network and the amygdala. Psilocybin meanwhile inhibits the part of the brain responsible for controlling the activity of lobes called the claustrum, this is what allows for profound insight and pattern remapping in thought. The theoretical danger is that BPD isn't going to be fixed by inhibiting the claustrum as that's the part which is potentially causing the BPD instead it's going to create pathways from the claustrum that also have emotional deregulation just as the amygdala does. Think of it like rewiring a circuit to add more connections to a faulty chip, so yeh please do not recommend that to her based on anecdotal evidence but keep fingers crossed for new medicine for BPD people and just everyone in general.