I'm not sure bringing her in is such a great idea yet, but it's silly to obsess about how she's different than the comics because no characters they've brought in from the comics are completely like they are in canon.
Smallville is developing its own canon and it's its own thing. They always put a different spin on the people and I usually like the results.
Yeah, she'll be different but so what?
Either you like the show and its characters as presented or you go off and watch something else on Thursdays at 8.