Going NC with toxic family takes a lot of courage and is sometimes the healthiest thing to do - especially with an NPD family member. I know it was a hard decision for me (I made it over 10 years ago!!) - the reason it's hard is because people don't get it unless they also have an NPD parent....so my struggle was with others saying "well I forgave my A father" or "I made the best of what I have". With an NPD it's about knowing the parent is not capable of change or empathy...or love. Forgiveness for me with my NPD mother is about acceptance - acceptance that she is incapable of empathy, change or even love and that her behavior will not change. She will continue to do everything she can to bring me down - hiring a PI, finding my employer and calling them and telling them lies about me - whatever it takes. Bringing me down makes her able to control me which is what she thrives on...it's her game....she can and will do anything to have it be all about her...and if I would fight it she would turn into the victim manipulating others by saying how mean I was.
So my decision to go NC with her was because her toxicity was keeping me from living a sane and serene life. And I'm glad I made it and won't be changing it in the future. Did I stop her antics? No way - she is NPD and she will not be ignored - so she continues to stalk me, hire PIs and try to get to me through other avenues. She found out when I moved, when my mother in law passed and that I got separated from 3000 miles away. I don't know how...HOWEVER it would be a million times worse if she had a voice in it all and was an active participant...so NC allowed me to make her a passive participant. Does she still upset me? Yes...but I'm working on that - HOWEVER, the NC has calmed my mind regarding her 1000% - I am able to see her for who she is and know my truth even if "well meaning others" with normal dysfunction don't get it and tell me to reach out to her - they do not understand and that's OK.
As far as her thinking she has "rights" to "her granddchildren" - well your state sounds very conservative so I doubt she does (here in my liberal state it's a different matter). So you as the parent get to decide if she is healthy for them or not and if she's not well she's not...and she will have to accept that.
Once you cut off those emails and texts you will be surprised how much your mind will clear and the gaslighting will stop as well. I became so much more confident in me once I went NC.
Just my experience - not all people with NPD mothers/fathers go NC but a lot do...so it doesn't make us bad people it just makes us people dealing with a bad situation in the best way we can.