Can the forbidden relationship that developed between the questioner and a married man, which caused her to become attached to him and feel longing and hope for a lawful union, become lawful in the future?

You must initiate sincere repentance from the forbidden relationship with a foreign man, for sins are a cause of deprivation of blessings and the effacement of blessings in religion and in worldly life. Continue supplicating, for Allah may provide you with someone better than him, and offer yourself to marry a righteous man whom you desire.