Personally, I have more thoughts about who Sam Jameson is not than who he is. I'm convinced that he is not someone that Amy is in love with or has any real intention of marrying unless at figurative (or literal) gunpoint. She clearly still loves Travis. Sam is not imaginary because his deceased body is there, but Amy is not grieving. That would lead me to think that he is not someone that Amy has or has had any strong feelings for. So the fiance is perhaps only for show for some reason unknown to us. The choice of the name of this character is interesting; it is the name of a female detective in a series of mysteries by Lars Emmerich. This could be a wink at viewers from writer John Christian Plummer or it could be a name Amy came up with as some sort of code with hidden meaning. I am hoping that in the 8th movie, Sam Jameson is never even seen, just heard about. I really don't want to watch Amy with someone else and Travis certainly doesn't. He appears utterly devastated, having lost far more than Amy has in this breakup. Travis said that he trusts Amy with his very life. I don't believe that she would abuse that trust.