The following passage follows the demonstration of Macomber's cowardice in the face of the lion. Make a list of events and ponder the implications that lie behind the precise details:
Macomber's wife had not looked at him nor he at her and he had sat by her in the back seat with Wilson sitting in the front seat. Once he had reached over and taken his wife's hand without looking at her and she had removed her hand from his. While they sat there his wife had reached forward and put her hand on Wilson's shoulder. He turned and she had leaned forward over the low seat and kissed him on the mouth.
"The Short Happy Life of Francis Macomber" by " Ernest Hemingway
This passage follows Macomber's attempts to reach out to his wife. Given that she ignores his embrace (holding hands) and instead kisses Wilson seems to indicate that she has rejected Francis and has reached out to Wilson. Thus, the passage is also a demonstration of Margot's reaction to Francis' alleged cowardice and her more accepting gesture toward Wilson.
Francis did not follow the lion to finish the hunt. Wilson had to do it. As a result, Francis felt like a coward. However, it is Margot who makes a point to dwell on this. Francis acknowledges his cowardly act but also tries to make light of it, saying that his face is red today. Then Margot replies that it is her face that is red, implying that she is more embarrassed than he is. Wilson, being employed by Francis, tries to ease his mind about the whole thing but Francis knows that Margot will never look at him the same way. Margot's gesture towards Wilson reveals her admiration for him (as well as her scorn for Francis) and she sleeps with Wilson the next night after retreating from another potential lion kill.
Even when Macomber feels transformed while hunting the buffalo, becoming braver than he was, his wife still looks at him with disgust. Wilson indicates that Margot killed Francis on purpose, although it is not totally clear this is the case. Just as this is ambiguous, the reader could interpret ambiguity about Francis as well: is it cowardly or reasonable to avoid an angry lion?
Considering that Francis did act like a coward (perhaps, at best a reasonable coward), and given the context of this passage, it is quite clear that Margot was embarrassed of, and for, Francis. Margot was also clearly quick to reject Francis and take up with Wilson. Margot's disgust is not a shock since their marriage was founded upon superficialities. He was with her because she was beautiful and she was with him because he was wealthy:
His wife had been through with him before but it never lasted. He was very wealthy, and would be much wealthier, and he knew she would not leave him ever now.
His wife had been a great beauty and she still was a great beauty in Africa, but she was not a great enough beauty any more at home to be able to leave him and better herself and she knew it and he knew it.
Essentially, they felt stuck with each other, each past his/her prime to find someone better. Margot's reaction to Francis' cowardice was an amplification of the way she had already been feeling about him. This doesn't really excuse her behavior (belittling him, sleeping with Wilson, and perhaps killing Francis purposely) but it does shed some light on why she rejected Francis and/or sought a kind of escape from her marriage.