Hoshi: Something called the Rom-illan Star Empire.
T'Pol: It's "Romulan"
In this scene, T'Pol is basically telling Hoshi that she is incorrectly pronouncing a brand new English word invented by Hoshi's translator to represent the Romulan word for their species.
Or that T'Pol is imposing the Vulcan word for the new species onto Hoshi - maybe Hoshi uses Vulcan translation algorithms in her Translation Matrix?
Or it could be that the new species actually calls itself "Romulans" - the similarity to Earth history a mere coincidence.
But it is a stupid scene, I agree.