I am such a fan of Polish names! 
[name_f]Klementyna[/name_f] and [name_f]Agnieszka[/name_f] are gorgeous.
Some of my favorites:
[name_f]Hania[/name_f] (although this is probably a diminutive of just Hanna?)
[name_f]Adela[/name_f]
Adelajda
[name_f]Michalina[/name_f]
[name_f]Anastazja[/name_f]
[name_f]Antonina[/name_f]
[name_f]Augustyna[/name_f]
[name_f]Celestyna[/name_f]
[name_f]Ewa[/name_f]
[name_f]Florentyna[/name_f]
Gracja
[name_f]Idalia[/name_f]
[name_f]Izabella[/name_f]
[name_f]Janina[/name_f]
[name_f]Julita[/name_f]
[name_f]Karolina[/name_f]
[name_f]Klara[/name_f]
[name_f]Leokadia[/name_f]
[name_f]Marcelina[/name_f]
[name_f]Milena[/name_f]
[name_f]Otylia[/name_f]
[name_f]Salomea[/name_f]
[name_f]Sybilla[/name_f]
[name_f]Tatiana[/name_f]
[name_f]Tekla[/name_f]
[name_f]Waleria[/name_f]
[name_f]Wioleta[/name_f]
[name_f]Zofia[/name_f]
[name_f]Zuzanna[/name_f]
[name_f]Zosia[/name_f]
[name_f]Halina[/name_f]
[name_f]Malina[/name_f]
[name_f]Ariadna[/name_f]
[name_f]Sabina[/name_f]
[name_f]Lilja[/name_f]
[name_f]Wera[/name_f]
[name_f]Cecylia[/name_f]
I agree on [name_f]Malgorzata[/name_f] - I have only ever come across one, but it feels rather old-fashioned to me as it was the sweetest Polish little old lady and she was gobsmacked I said her name correctly - her face lit up like a little child’s on [name_f]Christmas[/name_f] morning! It was the sweetest and most wholesome thing.
Good luck with your character!