The quote that you have identified comes after Mrs. Mallard has received the news that her husband has been killed in a train accident. However, although at first she is filled with "sudden, wild abandonment" as the "storm of grief" sweeps through her, reflecting upon her reality in solitude, she comes to change her reaction completely. Instead of being plunged into the depths of despair, she reflects on the freedom that her husband's death has given her and how precious that is to her. As she sits in her room, she looks out of the window and sees the following sights:

She could see in the open square before her house the tops of trees that were all aquiver with the new spring life. The delicious breath of rain was in the air.

Note how the tone of this passage is full of hope and new life. It is immensely significant that the season is set in spring, symbolising rebirth and the start of a new life--both for nature and for Mrs. Mallard. The tops of the trees that are "all aquiver" foreshadows the sense of "monstrous freedom" that she is about herself to experience. Thus we can see that the passage that you identified foreshadows the kind of "re-birth" that Mrs. Mallard experiences, that is unfortunately cut too short by the return of her husband.