Cutting her off was definitely rude, but I agree that it’s silly to ask everyone you meet if they wrote each book you want to discuss with them.

If you had something like

Alice: I’ve been researching a guy recently, do you know anything about him?

Bob: I recently read a book about him, have you heard of it?

Alice: I wrote that book.

Bob: Wow, cool to meet you. I really liked your work!

Bob still assumes that Alice didn’t write the book until told otherwise, but he doesn’t cut her off, and this conversation is perfectly pleasant.