I was talking to a psychologist fairly recently (she is a parent, we were talking at the side of dc football practice) and she said that if parents were able and willing, they were by some distance the best people to be "therapists" for their dc as they know them best and are with them more than anyone else, in case this interests you.
I don't think adopters should ignore what psychologists and a large group of adult adoptees are saying. I know adoptees into their 50s and what they say now is very different from what they were saying in their 20s and very different from what they said as children.
It is an imperfect situation as there is so little useful practical support, and obviously there is no "one size fits all" (and your situation sounds tough, as if the dc did ever want to see her it sounds as though that isn't an option, which sounds as though it would be incredibly hurtful) but for the vast majority of adopted children, having well managed regular direct contact normalised is going to be the ideal, I believe. At some point this will be researched well enough to convince even the toughest, I am sure.
No it isn't easy - and it is destabilising in the immediate aftermath - but in terms of the long term it is necessary if it is possible, and by possibly I mean objectively possible.
@flapjackfairy I have just realised what you meant by axe to grind. For full disclosure, not I am not a "birth parent", and none of my dc are adopted, by me or anyone else. I am also not against adoption, just slightly wearied by some of the diehard posters.
I am really out now! Good luck to everyone.