It looks like the crew member who painted the words Little Girl, then used the same paint to broaden and darken the forward boarder line to give a visual continuity to the letters. Visually it gives the size of the letter script a boarder to help it look like it belongs in that spot. Kind of like hand painted signs on houses and buildings in the US during that era. The painter framed the picture which helps draw your eye to the letters. Contrast that to the rest of the tarmac line up and you see the standard boarder is the thinner less obvious boarder line.
I think the authors of some of the color profile plates either never saw this large closeup picture or, themselves wanted aesthetic continuity versus faithful historic reproduction. Given the angle of the sun based on the prop shadow and what we know about the smoothness of the skin cross section at the juncture the line is following. That is not a shadow but an intentional widening of the line.
