Katie wasn't anywhere near skilled in the use of any blade... really she didn't have much experience beyond the occasionally play fight. Her Quidditch instincts helped, to an extent, if only to make her better at dodging and ducking. But mostly she was just play fighting with him, blocking his attack and then jabbing out with her sword. "I'll skewer ye, ye scurvy cur!"
"SQUAWK! T is a scurvy cur, SQUAWK!" Grinning, Katie swiped at him again as she agreed, "Aye, he is, Polly!"