"What does he feel for her?"
Translation:Cosa prova per lei?
Is "sentire" not correct or not usual in this context? Word Reference dict (https://www.wordreference.com/iten/sentire) says that it could be used for feeling emotions.
In case it is useful to someone, "che" and "cosa" are informal versions of "che cosa". The former is more informal than the second. Depending on the region of Italy, one or another is more usual.
"Sentirsi" is how one feels about oneself, i.e. "I feel fine" is "Mi sento bene", but "I feel pain" is "Sento dolore" or better "Provo dolore"; in this case the speaker is asking what he feels for someone else, so it's not talking about how he feels himself. Did that make any sense?