No, you seemed to be confusing them, by saying that Post-Crisis, Babs wasn't Batgirl. The Betty Kane Bat-Girl just plain didn't exist after the Crisis. (Neither did Kara Zor-El or Helena Wayne.) But Batgirl did. Saying she didn't because she was no longer active into the late 80s and beyond is like saying Bruce and Dick's parents "didn't exist" after the crisis because they only appear in flashbacks and don't actively effect the story.

And yes, you are correct. Far worse things have happened to Cass than Horrocks' run. It was not meant to be an insult to everything Horrocks has ever written; the "Batgirl and Robin" issue (I think it's #53 or thereabouts) is actually one of my favourite comics ever.

But Barbara Gordon calling Cass Cain "stupid" should never have happened.