Is it permissible for a woman to continue loving her ex-husband after her 'iddah has ended, given that she has not remarried and has been unable to forget him?

There is no sin upon one who loves her divorcee, for love is not something a person owns; rather, God owns it, as in the Hadith, "O Lord, this is my division in what I possess, so do not hold me accountable for what I do not possess," meaning the heart. However, if you despair of his return, it is not prudent to remain attached to loving him. It is a misfortune to love someone who does not love you. So occupy yourself with the remembrance of God and draw closer to Him, for perhaps God will replace it with a love for Him that will preoccupy you from loving anyone else.