Possibly be cheating?

Girlfriend of 3 yrs. Never any feeling of cheating. She says a guy stopped by her house, 9:30 at night, a courier from the town where she works. She see's him almost every AM, work. She told me that night. One week later he stops by again, same time. She told me the next AM. She thought it was weird and wrong. He is married and she knows the wife. She says over and over she will talk to him and tell him he is not welcome at her house. One week later she wants to come out to my house. I believe to avoid another visit. She has stated that she will not confront him but just avoid him and hopefully he will just go away. I have stated that she should confront him on it before hand butshe refuses too. She said she made a comment at work and he called her on it and stopped by the first time. I think the 2nd time is pushing the issue. Should I be cautious that she might be alittle more involved than what she is letting on? Or am I just being jealous?