Is it permissible for a girl to break off her engagement to a man she does not want and is not comfortable with, in order to marry someone she desires, who had previously proposed to her and whom she had asked to wait?

One should not accept a man's proposal initially if his situation is as described in the question. Terminating an engagement after it has been established is considered a breach of promise, a disregard for it, and a psychological harm to the suitor. Therefore, it is preferable not to terminate an engagement if the suitor is satisfactory in his religion and character, but there is no sin in terminating it. Al-Kharashi Al-Maliki said: "It is disliked for a man to abandon a woman he has become engaged to after proposing, because it is a breach of promise." He also mentioned that some scholars said: "It is not forbidden for a woman or her guardian, after the engagement has been established, to withdraw from it and choose someone other than the suitor." There is no impediment for someone else to propose to her afterwards.