This won't be easy to spin in a place like Georgia, even if Atlanta is a more sophisticated pocket, though it would be worse if it was Andrew bringing a guy into the fold rather than this circumstance.
In every, single story I've heard about people in an open relationship or open marriage it's only one of the original two who is into having more partners and the other person accepts it because they want to be with the other one so much. If it remains fulfilling for the one who remains monogamous, cool, but I've never seen it work out that way. Even if he's given a hall pass, it wasn't originally his idea or intention. I feel for Andrew and what looks like codependency, but I don't know more than anyone else here about their situation. It certainly looks like Amy has lived in a psychological bubble for a lot of her adult years. Maybe she didn't get to experiment when she was in college and now has a huge itch after being with the same guy for 25 years and no kids. I'm just glad my wife is into dogs, not cat.