The main character is really weak. It's really disgusting.
Who hurt you? This is a school full of children that were taken and trained as soldiers, expected to die before their 18th birthday. So you call a child in a lonely situation "disgusting" for crying because her arm got cut off? I'm sorry but what? I've heard some pretty insane things on these forums before, but this is definitely up there.
Edit: I genuinely don't like the idea that supposed weakness, which everyone has their weaknesses, is something that's disgusting. It's part of the nonsense narrative that men can't cry. Everyone gets stronger by acknowledging that they have a side of them that's not strong and that they can't be strong in every situation. People don't get stronger from others always beating them down and being toxic about weakness, crying, and strength. Compassion and Empathy are also great strengths.
She just heal herself from near death. It's probably just blood she didn't wash.
Yeah, her clothes were torn up, but some panels showed her boots were still intact. She showered, got a new shirt from the nurse and put her (still bloody) boots back on.
I think that last panel was only to show the discrepancy between their happy reunion, Shiina's ignorance about what actually had happened ('No injuries' - 'Nope [not anymore]') and the actual body horror Mimi had just gone through (she already admitted she hated the sensation of being chopped apart missing an arm).