Is exchanging messages via Facebook between a young man and a young woman, inviting her to commit to religious observance, considered an unlawful seclusion (khalwa)? And must it be stopped? What is the expiation for it if it is unlawful? And how can she be helped to commit to religious observance without committing the unlawful?

A man's conversation and correspondence with a non-mahram woman are permissible if done appropriately, and this is not considered a private meeting (khalwa). However, it is a dangerous باب (gateway). The preferred approach is to abandon it or to have a trustworthy woman supervise it. If a sharia violation occurs, sincere repentance is sufficient, and there is no specific expiation required.