Need advice on level of openness in adoption

We are in the process of adopting a 5 year old girl. It's kind of a long story, but I am very good friends with birthmom's step-sister. The girl was in foster care and bmom's parental rights were being terminated. The family talked to bmom about us and that we were willing to adopt the girl. We met with bmom and she agreed to sign over rights to us. She asked if she would ever get to see her daughter. We told her it would depend on what a counselor recommended. When we got custody the judge decided to keep the case open with DHR (even though this is a private adoption). Bmom's weekly visitation schedule was continued until adoption is finalized in August. S (our daughter) went to one visit with her bmom and regressed A LOT after it. We filed a motion with our attorney to get visitation stopped and it was granted. After reading her DHR file, we are uncomfortable with the birth mom ever having visitation again (there was no physical abuse, but lots of neglect and even death threats to the child). She is bipolar and has drug problems. Bmom is now driving my friend crazy with texts and phone calls (she doesn't have our contact info) asking when she will get to see S). She is pissed about the visitation being stopped and is saying she made a mistake signing her over to us (even though her rights were being terminated and S would have been lost to the state). I'm not against an open adoption, but I just don't know if it's right in this situation. (FTR, bmom's parents agree wtih us, that she shouldn't be allowed to see S). We are getting counseling and therapy for S because it is obvious she is grieving for her mother. I am going to ask the therapist what her recommendation would be. Does anyone here have thoughts or advice on what we should do?