Damian was totally fine with not "praising" Harley anymore than he already had, so he didn't mind her brushing things off like that. Still, though, with Harley's description of what Barbara must have been like, he can't help but point out:

"It's a learning experience. If she had made it to the end, she still would have had to kill someone if she wanted to win."

Meaning she'd have to get over that starving and scared attitude unless she wanted this to keep happening.