Actually, Grazy would not be used as a diminutive at all in Poland.
Grażyna (not
Grazyna) is pronounced gra-ZHI-na, and the commonly used diminutives are Grażka (GRASH-ka) and Grażynka (gra-ZHIN-ka).
masculine list:
https://www.behindthename.com/pnl/191050/124079feminine list:
https://www.behindthename.com/pnl/191050/124080