But her sister would have a solicitor already if she is this far into the adoption process wouldnt she? How would you get to this point without one? (genuine question )
I am suprised you say this in unusual. I dont mean that in a sarky way, I am genuinely suprised that this is your experience.
It happened to us and it has certainly happend to quite a few people we know in RL and online.
IME it has never got anywhere, the birth parents rarely turn up at any court hearings.
Technically it can halt an adoption and the child be returned to the b.parents but unless the adoption was ilegal I cannot imagine this happening. Even in cases where the child has been removed in 'error' the child has stayed with the adoptive parents.
Its worth the OP's sister calling the adoptionuk helpline if she is a member. They will be able to give her legal advice.
My DS's birth monther approaches solicitors on a fairly regular basis. It doesnt cost her anything so she can get them to write us a letter demanding contact. I used to contact them and say 'you do know this child is legally adopted dont you?' They were not aware because she would omit to mention that little detail. The letters are upsetting but they dont mean anything. She has no power whatsoever. She can get it taken to court but nothing would happen.
Its horrible but part of adoption. I dont blame her. Its her way of dealing with what she has done. She can blame us and the system for her not seeing her birth child instead of taking responsibilty.