Personally, I'm not too fond of those cross scars. They're too neat, and too artificial.
Unexpected lesson in how people actually care about her. Surprisingly wholesome. It only cost a few cheap stickers, and some guilt.
You don't really need that long nails to peel those off. It depends on how short you cut them, but I find it even uncomfortable to cut them that short.
She's also occasionally a somewhat responsible teacher.
I'm going to assume they meant that she's so skilled she took care of the scar well enough that it healed so quickly.