She chose the Katana for that... Which is a bad option for dismemberment. That's a slashing weapon sure, but cleanly cutting through bones would require a far more heavy weapon, like an executioner's sword, for someone who's lacking muscle like her. There's only so much that the sharpness of a weapon can do. If you can't cut through a Gambison with a Katana, what makes you think you can cleanly cut through bones? That gaudy double headed axe would've been a better option. We can just assume that somehow the modification to their bodies also modified their bones to be easily cut and broken.
Well either way. I'm happy to see that Momono survived. And I'm not surprised she just straight up murdered whoever was closest and convenient to kill, no morals about it, just gaming it out. She already won more than a dozen games, and while she did say this was a cooperative game, it indicates she's familiar with all sorts of games. It turning from PVE to PVP probably just switched gears in her head, that's all.
...
Basically girl is a psychopath.