How to defeat Kouzou:
1. She's invulnerable while encased. Avoid attacks and wait until she bursts open and lays down vines all over the arena.
2. Avoid the vines (touching them is instant death) and seeds popping out of the pods along them, while firing at her head in the center of the flower. You can also shoot the petals off to get a clearer shot.
3. After a few hits, she will withdraw the vines and close up again.
4. As her health whittles down, she goes from releasing two vines, to four and finally to eight every time she bursts open. She will also get more aggressive and try to knock you into vines more often.