I sat her down and we had a talk. It did NOTHING. It actually made things worse.
This will make things worse, as your MIL is afraid of losing control over her son, so wants you on side. She will provoke fear, but
My husband has advised me that you can’t get too close to her, can’t be vulnerable, can’t expect much, basically keep her at arms length.
Sage advice, imo. Avoid allowing her to divide and conquer you, keep a united front. Using the S.E.T. framework (Support, Empathy, Truth) when dealing with someone with BPD can help.
And now when she seems mad or leaves me on “read” my anxiety skyrockets.
Ask yourself what would happen if you do nothing ? Focus on reducing the fear she has manufactured (meditation, walks etc…) Sometimes going low to no contact is the only option. You don’t have to ignore her, just a brief text message (avoid phone calls and personal meetings) until you can weather it better.