Is there any point in responding?

[MrHT]

I'm sorry for what you are going through.  I have the same exact situation with my uBPD family member.  I eventually went NC about 8 months ago. 

From my experience (and failures), I would not try to justify yourself her.  That will do you no good what-so-ever.  I wouldn't lash out on her either (although it would feel good it would just fuel the fire).

She is trying to control you via FOG (Fear, Obligation, Guilt). 

If you choice to response.  Respond with how she makes you feel and set boundaries.   "Mom what you are saying makes me feel <insert feelings here> <Set clear boundary next> 

It is also PERFECTLY ACCEPTABLE not to answer at all.  Verbal abuse (which is what this is) does not need to be replied to.  I told my mother if she to verbally abuse me I would not response to her.  Since that is all she does I have gone NC with her since February.   It was hard but I was loosing my mind everything I received communications from her.  It was like PTSD would set in when I saw an unread message from her