Hey i already suggest that but i think instead of 30-40s we need to search the 60s beacause that is the time when Beth Doe comed to United State.I think I discovered a possible way to locate who Beth Doe may be. If you have ancestry or familysearch feel free to help me. Search place of birth Europe and then select the places in Europe where isotope test suggest she was from. Then in the residence area put in TN. Look at the names of people 1930-1940. Look at the names of those peoples' children. Then go to classmates website and look for pictures of those children to see if they would match Beth Doe. In the classmates search we would be looking for people from the southeastern part of the US who were in high school in the mid 70s. It might work it might not. This type of search would be based of the isotope test results for Beth Doe.
I already start to research and i'm focused mostly in Balkan countries like Croatia and Serbia,maybe we never will reach anything but it's worth a try