Why not use Mister Mxyzptlk as the villain instead of Selena?
I never understood why the Christopher Reeve produced Superman films never used Superman's rogues gallery from the comics outside of Lex Luthor and Zod. It seemed like, the producers felt that since this is movie about a female superhero the main villain should logically, be female also (since we don't want to see a big bad man beating up on a woman). Hell, they could've cast Dudley Moore as Mxyxptlk (he was rumored to be the top favorite had he appeared in Superman III based on the early draft) and keep his old comedy partner, Peter Cook as his sidekick of sorts.
http://en.wikipedia.org/wiki/Mister_Mxyzptlk