I tried showing her the source of each sound, when possible, but it doesn't seem to help. Her reaction is very specific - for example, the neighbour has SIX vehicles (yes, six - though only two people live there), and she only reacts to ONE of the cars when the driver slams the door. And my kitchen - there is ONE cupboard that she reacts to if I close the door when she is in another room, the other cupboards (all the same).....nothing. And, no, the cupboard that sets her off does not contain any food - just mugs and glasses.
Mags is a short girl, so not sure she can see out of any windows that would give her a view of street traffic etc (which is probably a good thing); I do take her outside to show her no one is at the door when she goes ape-sh*t at a car door slamming.