Well i mean, 18 was shown to get quite a big boost in power, to which she busted out of the Love Amour. She probably just, like you do in DBZ, bust out this random power increase, and now she she is comparable to 3-A. Its bs reasoning but we have accepted this before from Super. She's still not as strong as 17 though, but 3-A has quite a wide gap.
Not to mention she was the one completely shattering giant Ribrianne, although that form should have been much stronger, and knocked her out of Base form...which Goku, Vegeta and 17 failed to do. Ofc they could do that, but if you see, Ribrianne is basically unharmed by all of their attacks, she gets thrown around a lot and hurt, but she doesn't even bear a scratch, compared to that of Rozie and whatnot. Tbh, i agree with 3-A 18 for being able to beat her, as well as be in a Tournament that has all these casual universals. Her and 17 have only recently just gotten serious.
Also with the Katopesla thing...idk if we should say he would have stomped her honestly, she was recovering from her injury, and he had just boosted his speed by like 300x, it was probably a moment when she was off guard and whatnot honestly, but seeing as everyone else has been treating him like a joke, then i doubt he would have stomped her, maybe blitzed a little but i dont think strong enough to beat her.