Question: Do people with BPD have the capacity to forgive?
Forgiveness is a choice - I think one that involves complicated emotions. If we look at this in context of all choices and behavior- one chooses a behavior because it benefits them in some way. All behaviors have a cost and a payoff and if the payoff is greater than the cost, the behavior persists.
Why would someone choose to forgive rather than to not forgive? The "payoff" could be that it fits our values, or religious values, or to preserve a relationship that we value, or that forgiveness is part of letting go of resentment which is better for us.
So why would someone choose to not forgive - how is that more "beneficial" to them than to forgive?
This is my own thoughts- from observations. In the Karpman triangle dynamics, the pwBPD sees themselves in victim position. There's a "benefit" to this perspective and it is to avoid shame. To take accountability for one's actions- this can cause shame. PwBPD have difficulty with uncomfortable feelings, and can assume they come from something else, rather than their own feelings. If they feel shame, then someone or something is doing this to them. Victims are not accountable, you don't blame a victim. It's not their fault. Other people are either in rescuer or persecutor position.
From my own observation, there needs to be "evidence" for their feeling like a victim. Even in the absence of a motive, she seems find some "evidence" of intent to be hurtful to her. I can visit my BPD mother, do several nice things for her, and somehow she will focus on something I didn't do or she thinks I did wrong and assume some other motive to it.
The "payoff" for the choice to not forgive is that it becomes evidence of victim position and this is a greater emotional need than to have the benefit of forgiveness. As to whether or not they can forgive- I think it's more about their disordered thinking that makes them unable to do this. It doesn't fit their way of thinking.