The Ada area cemetery with many Rinehart graves is the Ada Valley Cemetery. While there are many older graves there well marked, there are many graves whose markers were made of sandstone and the dates and names are no longer legible, even if only from around 1900. I was just there today, and live about 40 miles from the cemetery. The next closest cemetery is a Luthren Cemetery atop Petit Jean Mountain, and that would not be a logical place for your Sarah Rinehart McQuilliams grave to be. I highly suspect Sarah is buried at Ada Valley Cemetery. I am a COBB and MORRIS descendant from the area, with Rineharts married into the COBB line.