Looking for1/2 sister born in Iowa 1958

Hello I am really new to all this and to tell the truth I never thought I would be looking for a family member . This last weekend I was told along with my younger sister, that we have a half sister born in Iowa city Iowa in may of 1958 which would make her 50 this may .I have been doing some research and have discovered ..........sealed records.....need a court order....etc My mother was forced to give this baby girl up at birthby her parents and she has struggled with the guilt and sorrow since she is now 71 years old and wanted to come out with this info she said she hasnt said anything till now because of the fear of what we would think and the shame she has delt with for almost 50 years. What my questions are .....where do I start ....what are my rights as a sibling...any help would be great Thanks Larry