Update with a mini-epiphany ...
Thanks to everyone for the replies. I've appreciated all the suggestions, including not chasing her when she runs away. But I've had to do so twice recently, once when she started running into the street and once when she ran over 50 meters away from me in a public park and was showing no signs of stopping.
Both times I was NOT trying to punish her. She just didn't want to do what I had suggested. I would gently guide her in the direction we needed to go, and she'd run away, wiggling out of my grasp when applicable, and take off like a bullet. And the expression on her face was almost manic, like she wasn't in control of how upset she was. She was almost like an animal running away from something that scared her, not caring where she ran as long as it was away. And I swear that I was nowhere near scary in those interactions with her ... no yelling, no threatening, no nothing. I'd been at a loss to figure out what's going on.
Then a couple of days ago I was putting books back on her shelf when I came across the title "When Sophie Gets Angry ... Really, Really Angry," by Molly Bang, that I've read to her for years. And it hit me as to what might be going through her mind:
"And when Sophie gets angry, really, really angry, she RUNS. She runs and runs until she can't run anymore."



So now I'm going to work on what to do when one is mad, and that running is NOT the answer. Wish me luck.