We got Krupa -- who moved from Poland to the U.S. when she was 5 -- in the Bev Hills ... where 'The Real Housewives' star told us she was a huge fan of her same-name sister.

"I love her. She’s Polish, of course I support her!" Krupa told TMZ Sports.

But when we asked if JJ could beat Rose Namajunas in their UFC title rematch ... that's when things got a little dicey.

"She can do it, she’s a Pol**k. Pol**k’s rule!"

"We're driven ... especially if you come from a communist country you have that in your blood."

FYI, the P-word ain't really the most P.C. term ... and Poland hasn't technically been communist in 3 decades.