The ones not affected are the ones eating her food?
If you're dying, you're usually not that picky about food.
"Western swords rely on weight to hit hard."
No. A Medieval long sword is roughly the same weight as a katana. Most swords are around that weight, with some small and nimble ones being lighter, and larger two-handed swords being slightly heavier. But not so much that even a weak girl couldn't lift one. That 5 kilo bag is much heavier. European swords were also just as sharp as Japanese ones.
Why is she surprised the super high-stat knife cuts well?