Your stories of how pets know people reminded me of something that happened to me.
Some years ago I had to have a production meeting at my house; three men came over, two staff people and a graduate student. After everybody sat down, I let my Golden, Irina, come to the porch. She went to greet two of them, looked at the third one-a very nasty,mean and petty person-and walked away without even wagging her tail. Either she knew how I felt about this person or she reached her own conclusions.