All of the ballads are in Child in some form therefore are readily available. What Sigrid's book does is show us and compare the variants Mrs. Brown supplied at various points demonstrating that these texts were fluid in her mind. Child regarded her ballads as supreme examples, but that was from the point of a Professor of Literature; a folklorist or ethnomusicologist might look at them differently. If I remember correctly there are certain episodes/events lacking in her versions (violence for instance) that occur in almost all other versions. Did she consciously edit them out? I think there is some mileage in regarding Mrs Brown as a collector as much as a source singer. She certainly came from a very musical, well-heeled family. Her father was Professor of Humanity at King's College, Aberdeen.