Since you didn't mention in what part of the US Ruth was located I have two possible finds.
If my research is correct Ridlin comes from the Ridlon/Ridlen Family name (1717-present) starting in the Saco River Valley area in the state of Maine. I was researching the Ridlon Family last week and in Sweden Maine there is an area called Ridlonville. Also there you can find a Ridlon Cemetery. In that cemetery there are tombstones for a Ruth Ridlon and Phoebe. I don't know if these are who you are looking for. I have taken pictures of many of the stones but not these two. The name Phoebe stuck out.
Also, a Ruth Ridlen was born in Hollis ME in Aug 10, 1790. She was one of 12 children. She was the second daughter of Abraham Redlon. She was taken from ME to Ohio by her parents in 1800. She was married to John Robertson in 1816 and lived in Adams, Decatur County, IN where she died in 1870. Her husband was blind for some years, and her life was one of trials. It is said she was a good, patient, devoted servant of God, and is now at rest. A portrait of this women was in the collection of G. T. Ridlon (1885). Sorry to say I have been unable to locate the collection.
Again I don't know if either of these are what you are looking for. Good luck
http://www.healthcycle.com/ridlonhttp://www.healthcycle.com/ridlon I posted 5 or 6 pictures for my family on the above site. Ernie Ridlon-Kozlowski Proud Descendant of Mangus Redland