I don't have BP, but I saw this on the listing of new posts and was interested in the answers. I use IFS treatment to help me with my DID (dissociative identity disorder). My T's have also said that some PTSD clients also use IFS to work with "ego states" or their "inner child" or the different aspects of themselves if they have what some would call "multiplicity" (as opposed to the dissociative disorder). The goal of IFS, as I see it, is to connect different ego states or parts of self with one another - to feel more whole, to be more present, to be more connected to the here-and-now, and/or to be more co-conscious and grounded instead of dissociative.

It would depend on the symptoms and comorbidity with BP, but I could see how IFS therapy might help with the existential nature of BP symptoms.

Have you thought about asking your talk therapist to try IFS therapy on you? You could state why you think it might help you, based on what you've read and understood online. You could also ask for a second opinion from a different kind of therapist who is more familiar with IFS therapy and comorbid mental health disorders.