User blog comment:Dtngfan/Wondergirl/@comment-1038387-20120225232846

Don't trust Wikipedia. Especially when it comes to YJ. What we know about Wonder Girl is that:
 * 1) Greg & co could not use her for season 1 for legal reasons of some sort.
 * 2) Those objections were gone when production of Season 2 began

What we don't know is if she'll actually appear, and if so, which version it will be.

I think Cassie would be easier to explain, Donna being a sort-of clone and all, though a combination of the two could also be possible - Donna with Cassie's origin, or either with an entirely new origin.