wouldn't it make sense just to use Supergirl
Too similar to, and too soon after, Smallville
. (And that would've been true even if there hadn't
been a Supergirl on that show.) Not gonna happen.
Having Smallville didn't keep them from doing Superman Returns. Maybe they're hoping that building up the character on TV will help sell her to movie audiences, even if the continuities are different.
But the fact that Smallville
started before Returns
was actively planned is a key difference. Also, neither really trod on each other, as the general Superman origin is both well-known and stable. A new, live action budget-friendly WW, on the other hand, could very easily muck things up for her depiction in a JL