"The Christmas Spirit" joke

This is supposedly a true story, told to me by a second source.
An older woman was cruising a busy parking lot just before
Christmas in her new Mercedes-Benz looking in vain for a
parking space. She finally saw someone loaded with packages
heading for a car, so she followed him, put on her blinker and
waited patiently until he pulled out. Just as he pulled out
a young man in a sleek black Porsche zipped in to the space ahead of her.
She was dumbfounded and outraged, and jumped out of her car, shouting,
"How could you do that?
Didn't you see me waiting there with my signal on?"
to which he replied,
"That's what happens when you're young and fast."
As the young man was about to enter the store he heard the
hideous crunch of metal striking metal. He ran back, horrified, to
see that the woman had gunned her Mercedes and smashed it into his
beautiful black Porsche. He ran back and cried,
"How could you do that?" to which she replied,
"That's what happens when you're old and rich!"