The narrator gives the reader no clue as to who is saying which thing or who the instigator of the conversation is.
She write everything down in her book thing.
The correct sentence is "facts and opinions are not necessarily in opposition". That is so because one can agree with a fact.
On the other hand "fact" may not be a synonym of "opinion". In research you can use "facts", "opinions" or both. It is so because one does not exclude the possibility of using the other. They are not necessarily anthonyms/ opponents. an opinion is not more important than a fact, but on the contrary, because facts can be proved easier than opinions.