I would really appreciate some advice on this. Sorry that this is so long.
DS and I fell out 2 years ago. The initial silly argument was 50/50. I stupidly thought that we could sulk with each other for a week and then have a chat and get over it.
It didn’t happen that way. Every time I tried to speak to her she had another reason to be mad at me. It was like she would go away and find another reason to be Mad at me. It was clear that she harboured a lot of resentment towards me.
I tried to resolve it with her several times but It was clear that she wasn’t interested. It became harder as she included her adult children in the argument who also called me to question “my behaviour” At this point it became clear that my sister had some kind of victim situation going on and from what my nieces said, she had lied about what had gone on between us. She also ignored my children and I was sad watching them be upset by it.
I messaged my sister to say that I would not continue to be abused by her and if she could not find a way to come to a middle ground, I would rather be NC. She never replied but blocked me on social media. I had my answer.
Since then everytime that the subject has come up with my Mum, my mum has indicated that my sister has wanted to resolve the situation but can’t as I went NC 
I did feel that even with me stating NC, if my sister really did want to reach out then she could. However I thought maybe she had changed her mind and was too proud to contact me and so I reached out again.
She was happy to hear from me but basically communicated that she was glad that I had come to my senses and it was clear that she still feels that it was my fault but if I am happy to apologise than she is happy to accept. I apologised several times for everything she came at me for when she did but now it seems she wants an apology for the NC.
The thing is even though the thought of not having her in my life makes me feel sick, I am not sure that I can rebuild a relationship where I am the one apologising all the time. Sadly I feel that after two years, if she is still unable to see that she played a part in all of this then she never will.
However now she is sending gifts to my children (I never stopped sending to hers but she has not bothered with mine at all) and the rest of the family do not understand why I am still cautious. I have told my mum that the last part of communication with sister confirms why I was correct in going NC.
So am I wrong? In two years, every form of communication has been instigated by me and she has not taken any responsibility for any of it. Or am I letting pride cloud my judgement and should I reach out once last time and just accept the situation?