Is OTHER wrong in the post ? POST : Long story with a lot of background

TL;DR Mom abandoned family and left me alone, didn't speak for 25 years and now her 'new family' are harassing me for not attending her bedside.

Throwaway for privacy but I was born in America and now live in EU. I grew up with my abusive mother, alcoholic father, twin brother and younger sister. Mom would constantly be screaming, shouting and demeaning me and my brother, call him Dave, by calling us rejects, unwanted, disgusting. I remember when I was 4 she dug her nails into my wrist she drew blood because I spilled a glass of milk. She scared my brother so much he'd often wet the bed (that we shared) and we'd be slapped silly by her and shoved into a cold shower to clean us off. Teachers often noticed bruises and such but after meeting our Mom, they'd back down out of fear for that psycho. Dad was usually drunk and while he wasnt abusive, he neglected us by not doing anything, and I mean anything to intervene or even say something to comfort us. 
Sister, Lydia, was a saint and was spared this abuse. As we got older the abuse just kept going until Lydia died in a car accident. Immediatley me and Dave feared for our lives as we knew Mom would snap but instead, she just left. No note, no warning, the day after Lydia was buried she was gone. We were around 8 when this happened. Our Dad was not a good caregiver but we were no longer afraid or being hurt. Sure we went hungry and our clothes stank but I adapted. I learned to cook, do laundry and looked after my brother but as we became teens, the trauma and continuing neglect was making Dave very depressed. He began self harming, thinking Mom was right to punish him for being worthless and when we were 15 he committed suicide. I  wanted to die when I found out. I blamed myself. I went out for two seconds to the store, my Dad was god knows where, and Dave didnt even hesistate. My Mom was at the funeral briefly but we avoided one another.
I've made peace with the fact he was very depressed and I truly did all I could but I blame my parents. I was taken into foster care with a nice family till I left for college. I havent spoken to my father in 15 years and my mother in 25. I left the country and hope to never see him again.
Last month, I got a contact request on FB with a message from a friend of my mothers from years ago. I thought this was weird as I barely remembered her. She said she had heard my mother was dying and that I should go say goodbye. I ignored the message.
A week later I got random messages from 2 girls saying they were my half sisters and my Mom gave them my name to find me. I politely told them I was sorry their mother was dying but not to contact me again. They flipped their shit and called me scum, she was right to leave me, drop dead etc. 
BLOCKED.
Then they started contacting friends from FB, tried to find out where I worked, made new accounts to send more nasty messages and even put me on blast to my old hometown FB page using fake accounts. I deleted FB but not before hearig my mother was dead. 
This all has dragged up so many feelings but deep down, I feel guilt for not seeing her and maybe I should have tried reaching out? I'm so messed up and confused but was I the asshole to basically ghost her in her last days?

