Marc Davis drew this study of a young woman in a reflective mood when he was twenty-eight years old. The US had just entered WW II, and perhaps she is thinking about her boyfriend or husband, who was sent overseas as a soldier.
The context of that time and the overall mood tells me this kind of a story, but it's just a guess.
Walt Disney sure employed some remarkable artists like Marc, who helped to transcend early animation into the art form we know today.
I really like this drawing!