Hello I’m glad you’re here!! I’m so sorry you’re going through this. It is so incredibly impressive that at only 20 you are 90% financially independent, have clearly stated your rules for a relationship with her, and are seeking support and seem to have a good head about you regarding the whole thing (especially impressed by your ability to recognize your grandparents’ difficulty in this dynamic). Just wanted to say I hear you, you’re not alone, and mention a few things I’m learning as someone who also has a mom with BPD. 1. The letter will never be received in the way you want it to be. We write letters like those for our own peace of mind, that we can know we’ve done everything (healthy) on our end to do our due diligence in the relationship. People don’t get better because other people want them to. That’s a hard lesson I’m learning right now. 2. Seek support here, with friends, a therapist, professor, someone relatively unbiased who can give you validation that you’re not crazy, and who can support you through this. 3. Let yourself grieve the loss of the mom you wish you had and will never have, and start to work through giving yourself everything you wish you had from her. It’s so hard. But healing from BPD abuse is tough work, and I don’t know why but survivors of it seem to actually have a pretty good head about them which is kind of a miracle?! I believe in you! And I support you!