The only thing she could say was.."Well, they did it in the 1st Century."
This is a lie. 1 Corinthians was talking about EXTREME, open, flagrant, immorality that would be recognized by people outside the congregation as such. It was not talking about matters of conscience or convuluted doctrines that people outside the congregation would not recognize as "gross immorality".
The purpose of 1 Corinthians 5 was to keep the congregation free of EXTREME immoral influences.
The WTBTS has expanded this to include deeply personal matters that would never become known to the congregation, let alone people outside the congregation except for the gossips known as elders' wives.
And this "not eating with such a man" doesn't mean that you treat them as if they no longer exist, it means that you don't SOCIALIZE with them in an overly familiar way.
There is a huge difference between say an engaged couple who have sex before marriage and someone openly living in a clearly sexual relationship with someone they are not married to. The engaged couple would not be disgracing the Christain name because it would not be widely known that it happened. That is unless the couple asks the elders for help and the elders' wives find out about that, then it will be shouted from the roof tops.
The WTBTS has twisted this principle into something horribly grotesque. They are liars.