Starlady, thank you for your kindness and encouragement. I have no doubt that the current situation is caused by the DP, as we were close before then. ED said that I was her best friend and role model, but there was a gradual emotional withdrawal, until the severance.
In a way I was expecting it as well as dreading it, because her DP used this method of control on her in the earlier stages of the relationship - withdrawal, silence - he once made her drive a 200 mile round trip in order to appease him, after one of their many quarrels. There were aspects of his behaviour which I found very controlling and my DD did not seem at all happy, constantly in tears. It all came to a head when I asked him to leave my house when DD locked herself in the bathroom sobbing and he would not leave. I asked him nicely, offered to drive him to the station etc, but he just wouldn't go, so I told him that nobody liked him, he wasn't good enough for my DD, and that I would call the police if he did not leave. He did then go and my DD emerged a while later, in a terrible state, and then went after him.
I may have overreacted to the situation, but DD was in a previous abusive relationship, even though she was very young, not physical but emotional, where I felt that I had let her down by not protecting her, so this time I was the opposite. She has also suffered in the past with her mental health so is more vulnerable.
I have apologised on several occasions and everything was back to normal with my DD after a week. However, he has not forgiven me, even though he pretended to for a while, because they were wanting money. I don't think my DD felt like that but she has gradually become more and more under his influence. She doesn't have a job, lives in a part of the country remote from family and friends, whom she has also cut off from, and there are therefore no other influences but his. She has gradually become more and more alienated but, still young, my hope is that with maturity comes understanding. That's why I am interested in Cherries' explanation of 'splitting'. DD thought I was wonderful but, as DP became a god in her eyes who could do no wrong, I have gone from white to black in her eyes, there is no middle ground or shade of grey.
Cherries and Smileless, thank you for your incisive posts. Cherries, you sum up perfectly the situation, the feelings, the anguish and bewilderment. I just wonder how the AC feel. It can't be that easy to cut off your parents or even your whole family, can it?