UFC's Mackenzie Dern: My Hype Train's Gonna Steamroll Amanda Cooper, 'Choo Choo!'

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!