Annette Bening was seriously undercasted

I think I agree, I just re-watched this for the first time since it came out, and the one thing that impressed me most this time around was Bening. Such a minor role, nothing particularly great about the character... but I dunno, she just kicked ass somehow. I think she's an underrated actor in general.

I think there are some filmmakers who are held in such high regard that nearly every actor and actress is willing to work for them in any capacity, even if it's a small bit role. People like Martin Scorsese, Tim Burton, Quentin Tarantino, Robert Rodriguez, Wes Anderson, etc. command such respect that they have the luxury of employing massive, ensemble a-list casts in their movies.

Her role wasn't nearly as insignificant as poor Glenn Close's role though. And that upset me---I watched the movie mostly for Glenn!

Please excuse typos/funny wording; I use speech-recognition that doesn't always recognize!

Of course she was, that was part of the satire the movie was going for - Casting a major actor or actress in a small part in an otherwise big movie.

This film is a dark campy comedy, much like "Doctor Strangelove". Burton is known for making hit movies that don't follow a beaten path. She was smart enough to get on the boat, put her tongue in her cheek and go for the ride.