Count your blessings. You are a bit ahead of me... because she is doing research... and has at some point been diagnosed... .
Mine is stone cold sober about believing I am 100% the problem... and she is the victim... . or something like that. Can be very convincing.
Can I ask some questions?
Any kids?
Might be good for a while to lay of pressure on her and focus on learning. Then... . when you starting doing limits... . I wouldn't make a big announcement. Just do it. They will figure it out. It's not a punishment of them... . it is what you do for yourself. If it impacts them... . so be it.
If you do say or explain anything... . take a deep breath... . say it once... . done repeat... . make sure you are clear. They will want to act like they didn't hear... . argue... . etc etc... . they are looking for drama. Don't give it to them.
Note: This doesn't cure them... but protects you... and I bet lowers the temp in the relationship.
Last: I'm still on the newer side around here... . so make sure and bounce my recommendations off what others have said.
Hang in there... . I saw benefits from limits. I was much less reactive.
thanks Form and Boss... . this site has helped me allot... Boss wish I could convince her to get help... we or she has been 5 different ones for help... one who diagnose her twice... started dpt but the word self harm and suicide came up and she bolted... . now she says it doesn't exist but I see on our laptop where she is reading up on BPD on line... . but you are both right I need to work on the one that matters and I can fix and that is me... . or get thicker doors and walls so I cant hear her scream those things at me when I leave the room...