I still however consider ntr to mean, you two are in a monogamous relationship and someone steals one of you away. Otherwise its cheating only.
However, it seems that most peeps think ntr is any girl in game doing anything with anyone other than mc. Thats not ntr. Thats life. Lol.
Since goblin wedding doesnt remove her from us i dont think its ntr. I would at most consider the wedding to be cucking the mc. Thats still not ntr.
However to be fair, lets address the mayor's wife. She comes home to her husband still. She stays with him so i dont consider that ntr either....just cheating....and having mc's baby. But she stays with the mayor (mind you, i havent completely caught up entirely with the game yet but im pretty much there i believe)