The three main characters represent different degrees of feeling and sentiment.
The student is in love with being in love. He speaks of love much like the courtly lovers of old:
"Ah, on what little things does happiness depend! I have read all that the wise men have written, and all the secrets of philosophy are mine, yet for want of a red rose is my life made wretched"
He imagines how he will hold his love if he brings her a red rose as a symbol of his devotion to her: "She will lean her head....and hold my hand." But, if he does not have the rose, he fears that she will "pass me by."
When this romantic young man brings the beautiful red rose for which the nightingale has sacrificed its life to the pretty young daughter of the Professor, she rejects it because it will not harmonize with her dress and a wealthy young man has given her jewels.
But, it is his reaction more than hers which is the most telling. He has no more appreciation for the beauty of this perfect rose than does the selfish girl to whom he has tried to give it. He has only desired it and said all that he has in the hope that she will adorn his arm. For, as he leaves he says, "What a silly thing Love is," indicating further the superficiality that belies his words, words which the lovely nightingale, sadly, has believed to be heartfelt. Furthermore, he tosses the rose away because he has only wanted it to win over the girl, not for its beauty as the nightingale had thought.
Nor does he appreciate the nightingale. He callously writes in his notebook:
In fact, she is like most artists; she is all style, without any sincerity. She would not sacrifice herself for others.
When the Student brings the girl the beautiful red rose, he asks her to wear it, with the intention of then telling her he loves her. But she dismisses anything romantic, saying,
"I am afraid it will not go with my dress," she answered; "and, besides, the Chamberlain's nephew has sent me some real jewels, and everybody knows that jewels cost far more than flowers."
She proves herself shallow and materialistic.
This little bird embodies all that the others lack because she is willing to die for love. She tells the rose tree,
"Yet Love is better than Life, and what is the heart of a bird compared to the heart of a man?"
Unfortunately, her sacrifice is wasted because she has been an idealist who has allowed herself to be deceived by the superficial sentiments of the Student, who merely mimics romantic phrases he has probably read.