In the scene where Jimmy has kidnapped Gillian and Sally is driving, he is rambling on about something and Gillian leans forward to tell Sally that the belladonna is in her bag. Looking in to the car, Gillian is sitting behind Sally, but when she leans forward and looks into the mirror, she is on the other side of the car.
I think that in this shot, because they are witches, Gillian is putting an image into Sally's head. I don't think Gillian moved or said anything out loud, she just made it so Sally could see and hear Gillian in her head. That's just the way I saw it, but I may be wrong.
She put the image into Sally's head...they're close sisters, and witches on top of that. A few times in the movie Sally can hear Gillian talking to her from long distances, so why wouldn't she be able to do this?
Yea, I noticed this too. I figured it was just an image that Gillian put in her head or something. I mean for one thing wouldn't the guy have noticed when she leaned forward and whispered in her ear. And besides it kinda looked like a visual effect, it didn't look too real.