Is it permissible for a girl to break off her engagement to a man who has done nothing to displease her, in order to marry another person whom she loves, and to whom she had previously asked for approval concerning the first suitor?

The relationship between a young man and a young woman before marriage is not condoned by the religion. Therefore, you must sever this relationship and repent to Allah. It is not permissible for you to propose to the girl until her engagement to the first suitor is dissolved. If she retracts her acceptance and inclination towards her first suitor, then you may propose to her at that time. This is supported by the hadith of Ibn Umar, agreed upon [by Bukhari and Muslim]: "A man is forbidden to propose to a woman already engaged to his brother, unless he gives him permission or leaves her."