(sorry, no chn inputs)
It is about decreasing the collision possibility.
The aisle in shopping center is always busy and with lots of moving targets and changing situation. It is MORE likely to lead to collision if you do reverse towards the aisle which comes with limited watching of all of those harzards.
In LZ'case, if she tired to park the car head out, the other moving car could be perceived earlier, and potentially avoided. In worse case, she would probably be in a better position of the argument if the reversing car hits her car's front.