My aunt just got rejected for a tourist visa from Armenia. My mom (her sister) sent an invitation for her to spend the Christmas with us in California, but nothing good came out if. The weird part is that her husband is a US citizen living in the US, so she can easily petition for a green card, but she does not want to move to the US. She has a very nice home there, which she will never leave for anything. The invite came from my mom, since the husband was in Armenia just recently, so she was going to stay with us, not the husband, who lives with a roommate and does not have the comfort as we do. She was going to come for 2 months only to get away from the winter there. So we were sure that there is no reason that she would get denied because she can easily get a G.C. In fact, her daughter
They suspect she is going to come to the US and stay. The fact that her husband can sponsor her supports their suspicion since they likely think that she is trying to get around the proper procedure at the embassy. You need an attorney to help you overcome their suspicion.
You don't seem to understand the attitude/perspective of the US Consul.
They quite easily may be thinking that she is trying to get around the system.
Talk to an attorney about how she can better prepare a tourist visa application ... a letter of invitation has almost zero value.