But it happened because she's literally doing the job of a battalion all by herself. In her country she had support from other people. Here the other mages all act together, when they decide to act that is. But since she's alone now and the mages act when is convenient to them she has to act alone and force herself to go beyond her limits. Of course one would collapse after that, Jo matter how strong she is.
It's like saying a surgeon can do all the surgery himself because he is a SURGEON. Every thing needs a teamwork. Can you imagine a surgeon doing a surgery by himself, everything.?
It's so funny to me that the empress is seen like this badass powerful woman when girlie gets out of commission immediately after using 1 (ONE!!!!!!) ability. It just makes her look like someone with a lot of power but no mastery over it.
It would be ok if she was just tired afterwards, but nope. She fights 10 seconds, uses powerful ability and then gets exhausted to the point of sickness. Like????? It's happened twice now.