"Which woman is Žofie?"

Translation: Která žena je Žofie?

[EstaJohnst1]

how do I know when to use ci or ktera?

[VladaFu]

čí - whose
která - which

They are completely different words.

[BraY381424]

Is it a kind of correct sentence "Which woman is Žofie?". They normally say it like "What is she like?" or "Whose ... is she". "Which" is used with things, not people.

[VladaFu]

Nope, "which" is used with people as well. You must consider the meaning of all these pronouns. They are not the same.