I thought this too. EDIT: just went through the timings/videos again. Yes, time for her to fall asleep/pass out. Around 15 minutes later, correct me if i'm wrong.
I still don't know why she would get in that car 'consciously' willingly. If she was cold, why not go to Sainsbury's? Haven't people said it was still open?
I think it's possible she was in a state of drunken unconsciousness where she could be led, instructed, ie could still walk, but wasn't rationally thinking.
Someone approaches and says: hey, wake up, time to get in the car, and she just goes with him.