Hi Hopeful84,
Welcome aboard. I am sorry that are going through a difficult time. Also, I am sorry for your loss. Losing a loved one is very hard. Combining the loss with a lack of validation makes it even harder. Many of us have felt exactly the same as you do. You are not alone.
Learning how to communicate with a person with BPD (pwBPD) is really beneficial. Using communication tools gives you the ability to express your feelings or concerns in a way that is less triggering or argumentative to a pwBPD. Communication tools have been a lifesaver for me. I have discussed very difficult things with minimal arguing or triggering. Here is a link to help you get started.
Communication tools (SET, PUVAS, DEARMAN)There is a tendency to forget about ourselves when we are in a relationship with a pwBPD. It is really important for us to focus on ourselves first. I understand what it is like to feel emotionally drained. Having a support system of friends, family, and my psychologist really helps me. Do you have a support system?
Sharing your story really helps. Perhaps you can share more of your story so we can help you better?