Khulwah (being alone with a member of the opposite sex) is Haram (prohibited), even if for Ruqyah (reciting Qur'an and supplicating Allah to heal the patient). The Prophet (peace be upon him) stated,
"No man should be alone with a woman, or else the devil will be the third of them."
What is even worse than being alone with this man is spending the night at his house and staying for many days and nights. This is one of the ways leading to evil and corruption. A Muslimah who has done such thing must perform sincere Tawbah and refrain from this evil behavior. (Part No. 17; Page No. 64) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.