I have quite a fascination with this case, as you can probably tell from the amount of posts I have made to this thread. In fact, I think I'm the one who originally posted it here on Websleuths.
Ruth got along well with her family and had recently become engaged to a young man who lived in the Cleveland, Ohio area. She seemed to be doing well in school, although she had told her mother that she was worried about one of her classes, and that she was feeling very tired. Other than that, everything seemed to be okay with Ruth, except for the telephone calls she received from an unknown man with a "high" voice.
I believe that when Ruth snuck out of her sorority house, she was planning to meet someone. I think she walked to wherever the meeting was to take place, since she left her car behind. Either she wasn't going far, or the person she was meeting had a vehicle to take them wherever they were going. It is possible Ruth was pregnant, and your comments are accurate about abortions being very unsafe in those days. It is certainly feasible that Ruth went for an abortion, died during the procedure or shortly thereafter, and her body was disposed of.
There were alleged sightings of Ruth and a young man wearing a collegiate jacket, in Zanesville, Ohio, but I have never believed these sightings were actually Ruth.
Like you, I hope someday this mystery will be solved.
If you enjoy cases like this, two other favorites of mine are the disappearance of Alice Parsons from Long Island, New York, and the disappearance of Lola Celli in Columbus, Ohio. There are threads for both of these here on Websleuths.