Does Yichud apply to a woman who goes alone to visit a non orthodox or Gentile couple?
Answer:
For a non-Orthodox couple, the prohibition of yichud will not apply if the wife is home (see Dvar Halachah 6:7).
For a non-Jewish couple, however, the prohibition of yichud does apply, and the presence of the man’s wife is not effective in permitting the situation.
