... A friend did this with their sibling and has been encouraging me to do the same, but their sibling does not have bpd....
And that is the difference between a reasonably normal person versus one who is prone to repeated disordered acting-out behavior.
Of course, you can try that - just in case it works - but after a few times of the push-pull cycles continuing, you may have to accept the issues are far deeper than a quick fix can address.
Going NC (no contact) or LC/RC (low or reduced contact) may be what is required. As for BPD, it is known that the closer the relationship, the more severe the impact on our lives. While someone on the periphery or with only occasional contact may notice something "off", those closer are more impacted.
This is where
firm Boundaries are important. People with BPD traits (pwBPD) resist boundaries, so we must set our own boundaries, for us, for how we
respond to the poor behavior. Granted, this is not intuitive. A very simplistic format can be, "If you do or don't ___ then I will in response do or not do ___." For example, if the person is ranting and raging, your boundary can be to exit and say you'll return later when the other has reset or calmed down. It's not a fix nor does it cover every situation, but it's better than appeasing and allowing the poor behavior in your presence.
