Is it better to accept or refuse a visit from a Muslim friend and his unveiled wife, knowing that intermingling is out of the question for the family?

If there is no fear of corruption befalling the host's family due to the visit of a woman who adorns herself immodestly, then the visit should not be refused. This is because a Muslim is permitted to host a non-believer, and a disobedient Muslim is even more entitled to such hospitality. The host may utilize these visits to influence her and invite her to righteousness, while ensuring the prohibition of unlawful mixing is observed.