Re: One more thing... to Horrocks, whose run reads like he himself is vaguely contemptuous of Babs and it's bleeding through into his Cass portrayal
That is something that has bugged me about Batgirl, but hadn't quite seen it in that light.
I can sort of buy Cass being a little contemptuous of Babs, as she gets closer to Bruce. Because it's almost like a kid dealing with different parenting styles of two divorced parents: one is always worrying over you and nagging you to do your chores (Babs wants her to do stuff outside of being Batgirl, worries about Cass's social life, reading ability, etc), and then one parent encourages you to indulge in what the other parent expresses concern over (Batman bonding with Cass over the Mission more than anything else, wanting her to have her own cave, be something like a weapon, even though he does care obviously care about her).
Bruce becomes the "fun parent" and Babs is the one who nags and makes her feel like she's not good enough. Bruce never bugs her about learning how to read or making friends, because if she's working with him she doesn't need to. He can read, and cave-dweller that he is, for him working with Cass, Dick, Tim or Babs is what constitutes much of his social life.
But given that there isn't much of a solid resolution for the rift between Babs and Cass that builds there, the underlying sense ends up being that her relationship to Batman is more important.