The rose does not tell the prince that she loves him because she has a couple of character flaws. One of her character flaws is vanity. Her vanity makes her very boastful but especially very demanding. She boasts that her four thorns can protect her from tigers, and yet, she considers herself to be too delicate to be allowed to stand in the draft. Due to her vanity she demands a screen of the little prince and also a glass globe to be put under at night. In fact, in his narration, the prince explains that the flower's vanity began to torment him, as we see in the line, "So, too, she began very quickly to torment him with her vanity--which was, if the truth be known, a little difficult to deal with" (Ch. 8). In addition to being vain, she is also very prideful. She is so prideful, that she would prefer to "put the prince in the wrong," rather than admit she is wrong (Ch. 8).
The flower symbolizes femininity, and despite character flaws, men consistently love women. In his narrative, the prince regrets his decision to leave, saying that he should not have taken seriously any of the vain and prideful things she said. He says that he should "have judged by deeds and not by words"; he should have recognized that her returned affection for him was shown in how "she cast her fragrance and her radiance over [him]" (Ch. 8). In other words, because she made him happy with her beauty and her scent, he should have recognized that she truly did love him. Furthermore, he says that he should have recognized that all of the vain things she said and asked him to do were simply her way of getting attention from him, just as women often do. Therefore, despite her character flaws, he continues to love his flower because she loves him in return. He especially loves her because she does a great deal of wising up before he leaves. She asks his forgiveness, assures him that she loves him, and also shows inner strength in rejecting the glass globe and saying, "I must endure the presence of two or three caterpillars if I wish to become acquainted with the butterflies" (Ch. 9). Hence we see that despite her initial character failings, she truly is a loving and noble flower.