I'll just say that I liked Carla a lot in her role. She made Sally more likable and added a 1930s/40s/50s movie-star vibe a la Ava Gardner, Audrey Hepburn, Grace Kelly etc. to the role. I also think some of the pin-up shots she did for the movie were stunning. But she just made her a likable and sympathetic character with her short screentime and I enjoyed her cameo in Under the Hood as well.
Malin Akerman really pushed herself in the role. I don't think she is a terrible actress, but she is quite limited. And in any scene relating with her emotions towards the Comedian and some of her bigger scenes with Dan (like convincing him to take Archie out or saying she left Jon), showed some struggle to get there. She wasn't awful, but honestly another actress could have done better. But Akerman did not phone it in and she wasn't distractingly terrible, either.