I'd forgotten about Lilith. That was the closest Marland came to pure camp - there were other fun bitch types, like Tess, or Marcy, bur Lilith was the one who could have stepped into a John Waters film without much divergence. Sara Botsford could play serious with the malicious glee underneath. Even her big moment where she's on the catwalk and Duncan sees her, she plays in just the right way.
Regarding Iva, I think early on they were a bit better at othering her and playing up a certain refined trashiness in her, alongside the Snyders at large. Once Marland cleaned them all up by the end of 1986 or so, she became more of a generic, suffering heroine.