Watching Korra hit herself causes Dinah to reel back as if she had been hit herself. Hearing about it was one thing, but she really doesn't have any control, does she?

And now she's fighting to stay still as Korra stands, moving to leave. Chasing after wouldn't have worked on Mia, and it sure wouldn't have worked on teenage Dinah.

"I can teach you to defend against chi-blocking," she says steadily, just as Korra's leaving.