Is performing ruqyah for the fiancée alone sufficient for the fiancé to return if the reason for separation was the magic of separation, knowing that ruqyah for treating separation includes both parties?

You erred by resorting to sorcerers, for questioning them and believing them is forbidden, and you must repent. It is not permissible to accuse anyone of sorcery without proof. You may present your situation to a legitimate Raqi (exorcist) or perform Ruqyah (definition) on yourself with the Qur'an and the authentic supplications, such as the Two 마지막 Chapters of the Qur'an (Al-Mu'awwidhatayn) and Ayatul Kursi. You can seek healing with honey, Zamzam water, black seed (Habbatul Sauda), and Sidr (Lote tree) leaves, as well as verses that invalidate magic. Be diligent in your remembrance of Allah (Dhikr) and ask Allah to grant you a righteous husband. The engagement is merely a promise that is not binding, and the suitor is a stranger to his fiancée until the marriage contract is concluded. Your going out with him necessitates repentance.