That's because Barbara is the female version of Spike from a parallel universe. Like Dusk Shine is the colt version of Twilight, Bubble Berry for Pinkie, Elusive for Rarity, Butterscotch for Fluttershy or Rainbow Blitz for RD. If you want to read a fanfic based on the idea of another Equestria in the multiverse with swapped genders, I'd suggest "On a cross and arrow".
That's because Barbara is the female version of Spike from a parallel universe. Like Dusk Shine is t