Jenny Elsewhere

Creation
The name "Jenny Elsewhere" should be available for anyone to use in any way they see fit...but the character herself is a blank slate. How she looks, how she dresses, her character quirks, what her agenda might be - it's all up to the individual who wants to do something with the name. Anyone can create their own Jenny Elsewhere from the ground up.

I'd imagine that - whatever she is - she functions in some way as a "prime antagonist" to Jenny Somewhere; the yin to her yang and all that. This can obviously work in all sorts of ways. With Jenny Somewhere not existing in all universes (like Jenny Everywhere does), I'd imagine that Jenny Elsewhere would exist wherever Jenny Somewhere doesn't.

In a nutshell: Use the name, make up the rest. Of course, one is not required to follow the "Jenny Elsewhere" name and scheme, but it should be a fun idea that people can play with.