"Who is she?"
Translation:Quis est ea?
No. "quae" would be correct in plural, or as a relative pronoun, but this needs a singular, interrogative pronoun.
When we already know the person in question is feminine, "Quae" can be used for "Quis". It is also the relative pronoun and interrogative adjective.
Yes, "quae"- neuter nom/acc plural relative pronoun... but also "quae" - feminine nominative singular relative-- and sometimes, when the gender of the person is already known, interrogative