I will note here that in all of the cases I observed, the PC in question was not mind-controlled, possessed, or in any other way unable to control his or her actions. For some reason, this GM decided that he, and not the character's player, would be controlling the PC's actions.
I call that bad GMing - shouldn't a player be able to decide what his or her character says, does, thinks, etc.? Or shouldn't the GM at least consult with the player before pulling the, "Your character does this!" schtick?
(For those who are asking themselves, "Did she talk to the GM about this?" I did. Numerous times. Each time, he promised to mend his ways, and then lapsed back into his old habits, sometimes in the same game session. I eventually got fed up with beating my head against the proverbial wall and withdrew from his game.)