It was never a "BEEF" because Nicki never replied, it was just Kimberly making a fool of herself.....Nicki doest respond to negativity and she doesn't need the publicity!
It's not fake. "It's Nicki Minaj-Lil' Kimberly" lyric proves that they recorded it together at some point and it's on key, nothing sounds like a verse was added/edit to it for a mix/remix. They most likely did this song before Kim dissed her.
They have pictures together too, so it's not like it would have never happened.