I'm taking an intro Spanish class and we learned the phrase "qué es ella de ti" to ask how someone is related to someone else. "Qué" is the equivalent of "what". I was confused about why you wouldn't use the equivalent of "who"... I considered what would be appropriate in English but I'm still confused. I guess "what" makes sense since you're actually talking about the relationship and not directly the person. However, because a person is involved I think "who" sounds more natural; to me, this seems especially true in past tense. "What" also makes sense because the reply "it is complicated" seems to fit.
(Looking at a photo) Who is she to you? She is my grandmother|friend. What is she to you? She is my grandmother|friend.
(In reference to a dead person) Who was she to you? She was my grandmother|friend. What was she to you? She was my grandmother|friend.
Even if it is an awkward way to ask the question, which is correct and why? Not too sure how to tag this question.