Does Kiryuin Satsuki have any infused Life Fibers?
She is 100% human, but she carried artificial finger nails made with Life Fiber (it is more likely to be a hidden weapon rather than an infusion with Life Fibers).

Kiryuin Satsuki waited until the last minute (until Ryuko arrived at Honnouji Academy with Senketsu) to wear Junketsu. And her butler was continuously against the idea of her wearing Junketsu. When after a fight, Satsuki always had physical and mental stress on her body and mind, so she always tries to end fights as quickly as possible when she is wearing Junketsu.