I am using a GLaDOS line in a map with a choreographed scene. I have the GLaDOS instance in my map. But in the console when the line is called is says something like: could not find actor "glados2" and the line won't play. I think it might have something to do with the fact that it's one of the lines in co-op that only one of the robots hear.

You should be able to play all glados lines in SP. Do you mind posting your IO?

You need a generic_actor named glados2 to speak the lines.