"Žofie has six fingers on her right hand."
Translation:Žofie má na pravé ruce šest prstů.
Czech doesn't use possessive pronouns that much. The verb "mít" already implies that the hand is hers. She can't have six fingers on someone else's hand :D
And if you really wanted to add the possessive pronoun, it should be reflexive, i.e. "na své ruce", not "její". But even "své"/"svojí" is redundant here.