When Johnsy sees that the last leaf is still there, how does it change her mood?

Johnsy has been suffering from acute pneumonia. It seems that she might not recover. Her spirits are low, and she no longer wants to live. The already tenuous ties that keep her attached to the mortal world are breaking one by one. Johnsy is convinced that she will soon die. She also believes that when she does the last leaf will also die.
Yet, the leaf lives on despite the howling gale and driving rain outside. Johnsy's fate becomes more and more entwined with that of the leaf. When she awakens the next morning, Johnsy demands to see if the leaf is still there. Much to her surprise, it is. Johnsy now feels slightly embarrassed at all her morbid talk about wanting to die. She believes that somehow the leaf has stayed in place to show her how wrong she was for wanting to die. Her spirits raised, Johnsy asks for a mirror so she can see herself. She also wants to see Sue when she is cooking. The survival of the last leaf has given Johnsy a new lease on life; once again, she expresses her dearest desire to paint the Bay of Naples.