Torture, for some, might be spending five nights on a Taylor Swift-themed cruise in the Bahamas. But for Aubreigh Gniotczynski, a 26-year-old from Texas, it is a dream come true. Ms Gniotczynski and her husband—a “fan by marriage”—have each paid more than $1,500 to enjoy karaoke nights and fancy-dress parties on the cruise, which is not affiliated with the star. In preparation, Ms Gniotczynski has been busily making friendship…