Most likely Im the one that's misunderstanding, this isnt my strongest part of the rules, and Ive been trying to review them as we go.
I dont want anyone to be able to recharge it on the fly, no. If the item is crafted with multiple uses instead of 1 that would be fine, representing finite sub-reservoirs that can be independently tapped. But it doesnt seem right to be able to grit your teeth and suddenly come up with more Chi to refill it, not unless you are burning some other resource.
Yeah, that last bit's kind of an issue no matter how this thing works -- though every use of it comes with additional crash.
It could be, since she's a doctor and knows physiology, the item basically uses a spark of magic to stimulate her adrenal gland and that's what actually gives her a boost, and the crash afterward is the result of that.