Family Search has records for a number of Ruth Lothrops, likely all deceased, in census and other records. Perhaps one of these is the person you are looking for.
There was one obituary in the Los Angeles Times of Sep. 8, 1973, although it is pretty sparse.
GALLUP. Ruth Lothrop, step-mother of Betty Caputo, devoted aunt of Mllllcent Luth, great-aunt of James and David Luth and other nieces and nephews, cousin of Harry Underwood, Service 12 noon, Monday, at the Wee Kirk o" the Heather, Forest Lawn-Glendale. Friends may call at Rosedale Mortnary. 1831 West Washington Blvd. from 12 noon until 4 p.m., Sun-dav, Roseriale Mortuary, directors.
