My pet theory on why Piper got so sick from performing the Binding is that unlike other crystal uses, which only entail the drawing forth of the crystal’s own inherent power, the Binding requires acting on, and altering, another living being’s makeup/power/(soul?). And perhaps that in itself requires an equal and opposite weakening or corruption of the user’s soul. So, even though she was doing it for a good reason, to assist Aerrow in powering up to help their friends and cause, Piper was essentially doing something ‘against nature’ to Aerrow and draining herself as a result. Meanwhile Cyclonis, who was arguably already pretty corrupted and twisted, doesn’t have the same (or possibly as great of?) effects on her.
But I don’t know. It’s not really…clearly explained, beyond it being stated that the Binding is sorta ‘forbidden’ and bad for you. What do you guys think?