I'm thinking back to what Dominic Keeting said about Jolene Blalock at VegasCon a few years ago.
Paraphrasing - "In four years she never spoke more than two sentences to me that was not in the script."
Maybe she was afraid of losing control?
That's a shame if true and not said in jest. I know it's not always the case but I like to think that cast members on shows I enjoy get along and even share a friendship of sorts.