She was disliked, that's my guess.
I don't think she'll appear in Best Wishes.

The English dub aired this at the wrong time. As a fan that watches both the Japanese original and the English dub, there just wasn't that big of a sad impact for Dawn and Brock that Hikari and Takeshi had because the Japanese DP special featuring the return of the two characters aired a few days before the final DP dub episode. There really wasn't a waiting period that the Japanese had to see them again as most the fansite covered the Japanese return of the characters. If fans didn't watch the Japanese one, then it probably would have a more emotional impact.

English dub edits: http://www.pocketmonsters.net/episodes/1123#Edits

Brock's goodbye was really poorly handled. All he got was a 1 minute handshake at the end and that's it.

I think the problem is the writers spent most of the ep focusing on Dawn and Piplup, rather than Brock. Almost seems sad for Brock, since he was on the show for 13 years compared to Dawn's only 4.

Its really odd that Brock's goodbye was so low-key. It felt the same as when he and Ash split at the end of AG, only without Ash's "hungry" line.

I couldn'd agree more I saw the Japanese one back when it aired so I didn't get as emotional when the dub did air. it still was a good episode.