"Where does Corinna come from?"
Translation:Unde venit Corinna?
In this example, "unde" does not mean "where". In this example, "unde" means "from where", also known as "whence". Because no additional Latin word is needed to indicate the "from".
The English might be translated a bit more closely as "From where does Corinna come?" or "Whence comes Corinna?" But I haven't tested if Duo would accept either of those.
I don't know why (having forgotten a lot of English rules), but those forms to me feel antique, formal and yet correct; whereas "Where does she come from?" feels modern, colloquial and American.
It's possible that I picked up "Whence" from reading Tolkien and my brain fixed it as "From where", making those two forms Tolkienesque (in my mind).