Hi and welcome!
Most BPDs will not accept that they have BPD. But whether or not they accept it, as your psych said, there are many things YOU can do to make life better for your whole family. And this is indeed a great place to work on yourself!
Being co-dependant means you are too "connected" to her. You base your emotion on hers, you live in "her world". To live with a BPD, you need to stop that. You need to be emotionally strong, independant, and "in control".
There is a LOT of information here:
https://bpdfamily.com/message_board/index.php?board=36.0Have a read and post LOTS of questions... .