[spoiler]Yeah, well, she took it at a younger age than them, and remember, at least Kyouko had a happy childhood before her father went nuts and Higurashi'ed the whole family.
She was traumatized, but not broken by the revelation, since she had already made accommodations with her mode of living. The shock COULD kill her in combat though.
Mami snaps the other way. She thinks of herself as a hero of justice. Learning that she will ultimately be the same thing she hunts is critical damage. Shes also known to be unstable to start with, allowing herself to be completely distracted by Madoka's decision to join her and get Charlotte'd.
Yuma just let them focus on the present really. And also having a healer helps. Support casters are important, and she does seem pretty good at AoEs and the like.
The barrier thing, yeah, Homura's field is one, and on a smaller scale, all the sword/gun/etc conjurations are basically the same magic(see UBW). The body thing is what Sayaka has been using since Kyubey told her her body was basically a remotely operated drone, which, in turn is just an extension of the same magic to transform into their battle form. It stands to reason a simple extension would be to create a new, more combat capable drone body...except all these 'witch-grade' magic push you closer to a Limit Break. You can't handle the mental stress for very long if you use them, at least without a shitton of experience. Which Homura has of course.
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