"No one asked for your opinion, you filthy little mudblood."
Chaos erupted. The Gryffindors were in an uproar, eager to get their hands around Malfoy's neck. Mayumi marches forward with a cold expression.
"And you, Malfoy." She said dryly, "are a shitty, sorry excuse of a—"
At some point of time, she switched to Japanese, and it took both Fred and George to drag her away.
"—だからうさい, このアホのぶすやりちん, 側溝の中に溺れ死ねでも誰も気にしへんで, あほんだらぶ殺せ!"
I did study Japanese for a while, so I'm pretty sure that's correct. And in case you're wondering, Mayumi told him to shut up then called him a f-ing hag and a man-whore, and proceeded to say even if he drowned in a ditch no one would care, then she said 'f you idiot, I'll kill you'.
Plus, If you look for it, you'll see that she's got kansai-ben.