more hair covering

Question

My wife covers her hair when in public, or when other men are in our home. However, when in our home, my wife does not cover her hair when my father visits. From what I understand of post 5501, that is OK. When we visit my parent’s home, and my father is the only other man there, she does not cover her hair either. We assumed that the law was more concerned with the individual (father in-law) then the location (their house vs. our house). Therefore is he can see her hair in our home, he can see it in his home too. Is that an acceptable conclusion? Thanks