If I'm thinking in Polish, my "default" pronounciation is the same as in case of
Graziana. If in English, gray-shee-AH-nah. I have no idea whether it's correct or not, it's just what comes to my mind first when I see it.
I'm not a big fan of it, I like
Gratia though, or Graziela, our Polish Gracjanna (grah-TSYAHN-nah) or
Gracja (GRAH-tsyah). Although it has some charm too and a lot of energy which's nice.
It goes very well with
Sebastian imo.
My PNL:
https://www.behindthename.com/pnl/154777