Mackenzie Dern is clappin' back at her next opponent for saying she's gonna "derail her hype train" ... saying Amanda Cooper doesn't stand a chance when they scrap at UFC 224.
"That's good, I hope she tries to do that!" Mackenzie told TMZ Sports. "It's gonna keep going -- choo choo!"
Mackenzie took some serious damage in her Octagon debut earlier this month (check out her lower lip!) ... but is such a badass, she immediately requested her next matchup.
Dana White granted her wish ... and now Dern's taking on fellow rising star Amanda Cooper in Rio de Janeiro, Brazil -- her home away from home.
Mackenzie, the former #1 female Brazilian jiu-jitsu player in the world, knows Amanda's gonna be a tough out ... but told us it's GAME OVER for Cooper now that she's got a whole country in her corner!