The more they try to do to defend themselves in the situation as written above lacking more details, the more risk they take.
They got out of the situation by complying. Good for them.
Bad for them that he/she were in condition white going to the parking lot. Excellent lesson for us all. That is one important key right there.
If we play pretend and say that son's friend has CCW, the best IMO they can do is get behind the car, draw and fire. And that is fraught with problems
They risk getting shot moving behind the car and potential gun battle. Does friend have extra magazine if he needs it - 2 guns vs 1. How many rounds in carry gun. Does female friend freeze under pressure or "go with" friend behind car. If she freezes, this is enormously problematic. There are so many variables, its somewhat silly to continue. At 20 feet, my idea is REALLY stretching it.
20 feet, two guns, friendlies surprised? Ick!
Some people are willing to comply, others with fight under any circumstance. Right or wrong seems like a subjective judgment to me on fight or comply in this circumstance. Personal preference for risk and threat assessment.
LESSON: In parking lot at anytime, especially at night, keep a hard yellow threat level. Always. Especially now in this worsening economic deflationary environment.
My 2 cents