What is the ruling on the relationship between a young man and a young woman in this situation, and what is the ideal way to end the forbidden relationship without harming her, given that marriage is not possible?

The engaged couple must cut off the forbidden relationship and beware of following Satan's footsteps in communicating in any way, as this is a door to temptation. Let them be patient until the marriage is completed, if Allah has decreed it for them. It is not permissible to be lenient under the pretext of not hurting feelings, for Allah's pleasure comes first. Stating the Sharia ruling to the fiancée and setting boundaries is not hurtful; rather, it is kindness to her. The lawful way to exchange love is engagement, then a lawful marriage. It is not permissible to contact or exchange love messages before the marriage contract, because that is not permissible and leads to temptation.