I dunno, if you're going to count a superficial cut to the face as torture, you have to start counting things like Dinah punching Ollie off his feet or Bruce smacking the Cluemaster upside the head to keep him moving as torture, too. Minerva isn't even hurt by that, her only response is a big ole indignant WTF; Bruce breaking a guy's nose in a fight is more damage and more excessive than Diana cutting Minerva's face here.
(And Minerva's hardly either captured or defenseless. I still can't buy for even a second that that flimsy-ass coil of rebar could hold her in any meaningful restraint. Admittedly, though, that's probably either a writing oversight or a penciller failure, rather than an intentional indication of something more subtle in Diana's comprehension of the situation or Cheetah's behavior, so it's probably not relevant to the conversation.)