Is it permissible to continue a friendship with someone who claims to communicate with Muslim jinn to assist in Ruqyah Sharia, knowing that no polytheism has been observed from him, but he speaks of unseen matters that occurred in the past?

There is no harm in befriending a girl who is mostly upright, and whose companionship does not harm one's religion or worldly life, while forbidding her from seeking assistance from jinn for treatment or anything else; because the preponderant opinion is that it is not permissible.