There's only one parallel universe.
These things happen.
I figured someone might chime in on how I'm blaming only poor Bill for his indiscretations and abuse of power manipulating Monica into servicing his uber-manliness and astoundingly hollow ego in desperate need of constant inflating, so I tossed in "home wrecking hussy" as a hyperbolic mockery of their judgemental sensibilities. Plus "hussy" is a funny sounding word, and sadly underused, so the oppurtunity arose and I went with it.