Adoptive Mother's Feelings Of Betrayal

I can totally relate to this.One of my adopted sons was in and out of prison,always supported him and etc through goodness knows what. He took his life whilst on another prison sentence and I found out on social media.He had been in touch with his birth mother for 5 years and had said nothing,not in itself a problem as had always said he should find her if he wished.He had put her down as next of kin so the prison contacted her and not us ,gave her his possessions and letters I had written him.She took charge of funeral and etc and we were treated as outsiders. I have told prison they were very wrong not to contact us etc next of kin has no legal status and she gave up all rights when she gave him up for adoption. There she was lording it about as the 'mother' when she wasn't his mother and even saying she is entitled to compensation. No she is a not she only gave birth to him end of. Prison are now coming to visit me to discuss but don't hold out hope for any answers.