One of my sisters ghosted my mother, me, and all our siblings for over a year, with no explanation whatsoever. I have suspicions over what prompted it but will never know for sure. She had gone through phases of NC with me and another sister over the years but we would always eventually see each other at a family do of some kind. She does not 'do' confrontation so will never discuss why she (presumably) feels upset/isolated/whatever feelings cause her to just cut people out.
The weird thing is that during this time she kept in touch with our father, who she has known for more than 20 years is a nightmare.
She has since got back in touch with our mother and of course my mum has welcomed it because she wants a relationship and she wants to see her grandchildren. Prior to this ghosting my other siblings and I used to comment (to each other, not mum/sis) that my mum always 'towed the line' with this one sister and never said anything even slightly provocative in case she took offense, because we suspected she would just disappear if she felt offended by any random comment instead of addressing it. And that's exactly what happened (we think!)
I will struggle to ever have a relationship with this sister now. I live abroad so less likely to see her at a family party etc. Before I was always civil/friendly but I would find it VERY difficult not to say to her now that she caused our mother untold stress and anxiety, that my mum literally aged before my eyes, and that it is cruel to have behaved the way she did, and that waltzing back in again like nothing happened is frankly a little insane. But if I say anything like this, she will fuck off again and my mother will go through all that heartache again. So I just have to hope not to see her really...
For the record, she also has VERY different memories of all sorts of things than the rest of us do. Not just childhood memories but adult ones. It's like she creates an alternative world and a role for herself within it and casts the rest of us howshe sees fit depending on if she likes us or not at that particular moment. Very strange indeed.