Welcome and we get it. BPD takes its toll on a family. You are not alone. Here is some suggested reading.
https://bpdfamily.com/message_board/index.php?topic=338206.0;prev_next=next~ In my personal experience, there were many other things wrong in my former marriage, but one thing I own was my inability to see my then teen aged son as truly ill. Or rather , I misunderstood his mental illness entirely and thought I could love him enough to rescue him. I was the one who took him to psychs , etc , but I always thought he would get better and "grow out of it" somehow. After many levels of hell later with our son, we are both on the same page now.
We can't give specific advice regarding your marriage, but keep in mind the actions that are for the highest good for everyone in the family. In addition, you are as important as your BPD child. Life and safety must be preserved for all.
Some positives here-It is great your daughter is in therapy, that is huge. Try not to be too troubled by her blame. In the BPD's eyes, everyone else is at fault and the cause of their misery.
~Both of you agreed enough to realize she needed help , that is something.
~You are reaching out here .
~ Since you currently are with your spouse, is it at all possible for you both to reschedule things such that each of you has some " down time"? For example, spouse can be at home while you take an hour or so pursuing a hobby. This is important. You need to reconnect with yourself as your spouse will need to do the same for herself. Would this be feasible at all?
We need our own support separate from the BPD child getting her support. In my case I also attend al-anon meetings ( there are some online) in order to help keep the focus on me. It is so easy to get lost in the BPD tornado. I also have my own therapist( not sure how your $$/ health insurance is on that score).
Please write back to us as you are able.