Well said, Cherries, and thank you for the intelligence and insight which you bring to this site.
I particularly identify with the 'double bind' in my ED's behaviour. I suppose all of our situations are different but, in our case, we travelled a long distance to spend a couple of days with her (staying in an hotel nearby as no way would her DP see us or entertain us in the house, which was fine). We spent a lovely time with her and when we left she dropped us at the station, we hugged each other and she said that she loved us. The contact abruptly stopped for 6 months. We were completely ghosted as were all other family members. She didn't even let us know she was safe when one of the terrorist bombs went off in the city where she lived. Oddly enough though she did send birthday cards and has always sent mothers' day cards etc - signed by both of them although he had apparently decided never to see us again. Eventually contact sort of resumed and we have a lunch scheduled in a couple of months, with both of them.
For a while, I was frantic, depressed, even entertained ending it all (briefly as I would never let my DH and other DC down), woke up in the middle of the night every night, crying and in despair. And the endless self doubt, the feeling of failure and shame, but above all the grief. And I have been through the whole grieving process even though she is still alive.
For the first six months I chased her, sending text messages, leaving telephone messages etc, all of which were ignored. I felt so helpless and beaten down, even though I have always been strong. I lost my mother, my brother and my best friend in an 18 month period, so loss is something which I fear most, and it all seemed so cruel. I was angry too, all at the effects on my DH and other children, and for a while I felt like a victim.
I coped by going to counselling (not sure how much that helped but it felt like being proactive, keeping busy, joining a gym, keeping up with friends and most of all, through the love and support of my DH and other two DD. I also stopped chasing ED, but would send e-cards on her birthday etc (couldn't send a card because she wouldn't let us have her address). It is clear from the conversations which she has had - not many - in the last few months (and in two years since that last meeting), that she wants to be chased so that she can reject any overtures, presumably because it makes her feel wanted or powerful or both, or maybe that is what she is told to do by DP (apparently now DH although she has not shared that information directly). By stopping the chasing, we appear to be getting more contact not less, so I am assuming and hoping that she does want to have some relationship.
Anyway, although I love her always and very much want to rebuild the relationship, I have realised that it will take time - how much I don't know, but there is no other way. And I feel strong again, not a victim, but myself, which ultimately I believe is the only thing we can all do - be true to ourselves in the knowledge that we acted from love.