Can anyone help with boundaries in my reunion with my daughter?

I am a first mom from a closed adoption era. My “birth” daughter found me when she was twenty-one and that was twenty-two years ago. We have both struggled with finding a place in each other’s lives confounded by insecurities and fears of rejection. Her adopted mom had a biological child before she adopted, and I don’t know if that makes her case a little different from other adopted moms or not. I’ve been searching for some place on the internet to help me sort through the complexities of this triangle and have yet to find anything; however, I stumbled upon this website and read comments by first and last parents, and it seems to me that there are similar issues. My birth child has never given me any name, but expects me to be a grandparent to her children without stepping on her mother’s toes. I have made so many mistakes along the way–blindly trying to forge a relationship that seems stuck in all the pain. I just don’t understand the boundaries, and I really have been deferential to adopted mom, because she is the mom, but I just don’t know what I am. Any thoughts or recommendations for other websites would be greatly appreciated. Thank you.