At the beginning of the story, we learn that Elisa is in an unhappy marriage. While her husband is not necessarily a terrible person, it is clear that he does not value or appreciate her in the ways that she requires. An example of this is when Elisa tries to give her opinion on business and he ignores her interest. This unhappiness leads Elisa to really appreciate the attention that an unknown visitor provides.
The attention she receives from this travelling salesman makes Elisa change. She fixes her appearance and feels happy and energized. This is the first change that Elisa undergoes. However, she soon finds out that the visiting man did not feel the same way about her. The realization makes her sad and upset, and this is the second change that we see in her. This leads her to cry in the car, and feel more unhappy than she felt before.