Hi Keylime:Unfortunately, you don't have the power to fix someone. The only thing you can do is focus on yourself, how you interact and how you react.
We started going to counseling initially to address issues from her previous marriage which was very high conflict and resulted in her loosing custody of her only child. She characterized the ex as a narcissist and that may have been true.
Since she tells you that everything is your fault, got to consider that this is a replay of her prior marriage. Her ex might not be as horrible as she indicates, and she could be telling others the same story about you. Usually, if a woman loses custody of a child, there is some reason for it, especially since you are experiencing so many issues with her.
I brought his diagnosis up to her but she totally rejected his conclusion and said the problem was all me.
It never goes well if you tell someone they have BPD or BPD traits. Best to focus on the individual behaviors.
I continued counseling on my own to address these issues and began to seek healthy relationships with my family and friends apart from her. When I tried to set boundaries I was met with her anger
Unfortunately, most people don't accept boundaries with a smile. You have to be firm and consistent. It's common for things to get worse, before they get better. That is called an "extinction burst"
Good for you to continue counseling on your own. Stick with seeking healthy relationships with friends and family - hold that boundary. It's common for those with BPD to try and isolate their partner, which is unhealthy.
It's common for BPD partners to project their bad behaviors onto their partner. "You are the one with BPD". Continue to work on yourself and your communication. A good thing to master is validation/don't invalidate. It's important that you don't invalidate your partner's feelings by word, expression or body language. You don't want to validate something that isn't true. If you aren't comfortable with validating "feelings" in a given situation, then best to stay silent.
There are a lot of good communication skills to learn her, so check out the "Workshop" area. If you go to the large green band, at the top of the page and check out the "Tools" menu, that can be a good place to start.