So is she Shizuku or Kasumi I kinda dont know or is she both?

she's shizuku. She projected a dream world where she "became" kasumi because she (shizuku) didn't want kasumi to be dead (kasumi committed suicide).
in the dream world, that Zeus created using her loss of kasumi as a trigger, she's kasumi but once Marco destroyed Zeus's system the control on shizuku was lost and she became herself...is that making any sense?

I thought of it more as 'she' is Shizuku's Medusa, Kasumi. The Kasumi Shizuku remembers her as or how she would have been if not for that turning point.

And new Kasumi, through these experiences grows as a person, becoming her own self (agree w/ you there)