Is it permissible for a religious former fiancé to propose to a girl who is currently engaged to someone else, whom she does not feel accepting of, out of fear that the marriage to the religious man will not be completed and the engagement will be broken off for a second time?

A man may propose to a woman who was previously engaged and separated from her fiancé, if he was unaware of her previous engagement, because the default is permissibility until a prohibition is proven. Similarly, a woman may annul an engagement for a legitimate reason, and she incurs no sin for doing so. If the annulment is without a legitimate reason, it is merely disliked. If the engagement is annulled, the new suitor may propose to her, even if he knows that she was previously engaged.