My college aged daughter feels that everyone else needs to change in order for her to get better.
It seems like two things.
One is that she gets to be the victim. No change until you change means she is not accountable.
Two is that she may feel you didn't protect her, and those can be valid feelings.
If you are working to change the way you respond to her, it might be more SEt than seT, if that makes sense (support, empathy, truth). Meaning, you may find yourself listening, supporting, showing empathy, validating than you do correcting her perspective.
You can validate how she feels (support, empathy) while also gently re-stating the truth (I will decide who I have contact with).
I can't remember if it's Valerie Porr's book Overcoming BPD or Shari Manning's book Loving Someone with BPD -- one of them says that if there is a repeating request that is nonsensical, you will probably seT more than SEt. "We have discussed this before and my answer is the same."
She is just unrelenting when she has conflict and wants me to get involved.
In what ways is she unrelenting? Maybe we can help find some ways to de-escalate that don't create too much anxiety for you, especially as you try new ways of communicating with her.