Hey somethingmore: I'm so sorry about what you are going through with your mom. It feels good to vent, especially where you are apt to find some listening ears who can understand. You don't sound like a person with BPD.
People with BPD are hard to get into treatment. Sounds like you approached your mom from the perspective of depression. I'm sorry your conversation didn't go well. Most people with BPD have other things going on. Depression and anxiety commonly go along with BPD.
Have you thought about moving farther away from your mom? Living right above her has to be ackward.
You can't change your mother. It can be easy to get caught up with
FOG - DEALING WITH FEAR, OBLIGATION AND GUILT. By setting and enforcing
BOUNDARIES and using various communication skills, you can make things better for you.
Are you feeling a degree of obligation towards your mother, perhaps that you have a duty to try and fix her?
Check out the above link on boundaries. What are some possible boundaries you might want to set with your mother?
We look forward to hearing more of your story.