I still think I could reason with them. I'm thinking about calling them on the day that W flys there and asking for there help with the sitch: not with the M, but with the drinking and BPD. I know I'm not supposed to reach out to family members for help. what do you think?
I think an intervention is needed. If you think they would be supportive of that strategy, then yes, I would reach out to them. Maybe discuss it with an Al-Anon person first?