Other mistake: As Dr. Challis is sneaking to the console to activate the flashing pumpkin, the digital clock on the wall behind him shows 11:35. It should still be before 9:00.
Other mistake: When Marge Gutman accidentally triggers the laser chip in the Silver Shamrock tag, you can see the laser "tethering" to her mouth when she pulls back, instead of shooting out in a straight line. This movie never once hints at the existence of target-locking or mouth-seeking lasers.
Other mistake: Why is it that Marge only discovers the microchip in the Silver Shamrock badge when it drops on the floor in the motel room? Surely she would have noticed it when her son would have thrown the mask against the wall, and it dropped off? Any normal person would have looked at it to see how it would have attached to the mask.
Chosen answer: She was turned into one when she was captured. The robots didn't speak and if you notice that after he finds her, she never says a word. As well, she displayed genuine emotion throughout the film before she was captured, something the robots also never did.
I agree, she was a real person until she was captured. If she were a robot, I think Chalice would have found that out when they made love. Plus, as you mention, she had real emotions until her robot replacement was rescued.