All that can presently (December 2022) be gleaned about Marion Mosby from sheet music covers and by Internet searching is that she was presumably an American actress/singer who has been featured on just one work namely Under the Jungle Moon (1907) music by Max Hoffmann, words by Edward Madden and published by The Rogers Bros Music Pub. Co., New York, USA
Her portrait on the left is taken from from the same work.
Surfers are welcome to contribute any further information about this performer.