I don't think you can OnwardandUpward. It's such a huge betrayal especially when lies have been told to 'justify' the decision.
I do wonder just how much thought goes into this before hand and of course I'm not talking about AC who've estranged abusive parent(s), but those who are clearly being influenced by their partner.
As far as chasing them goes, you're damned if you do and damned if you don't. So often I've seen EP's here on GN be accused of harassment for sending an EAC a card, flowers etc.
I remember last year I think it was, an EAC posting that they were surprised at their parents lack of enthusiasm when they (the poster) having estranged their parents had decided they wanted to reconcile. TBH I wanted to say 'what do you expect' but refrained and talked about the difficulty for his/her parents in being able to trust him/her again.
You never expect it to happen at all, if it happens once you'll always I'm sure be terrified that it could happen again.
You're right about the Prodigal Son, the father knew it was out of his hands and when he did come back repentant, so much so that he was prepared to work as a servant, his father took him back as his son.
What's often overlooked is when the other son was resentful of the welcome his brother received, his father said 'our son was dead to us but now he is alive again'. I think that's really powerful and maybe explains why estrangement is often referred too as a living bereavement.
We do have to protect ourselves, just as AC who were abused by their parents protect themselves by estranging their abuser(s). That often raises the issue of unconditional love but not wanting to reconcile doesn't mean we don't love them, we do and that's the hardest thing of all.