So if you say something like "Do you want me to read this book?" would she say "Book." ?
Or would she say "Yes"? or "no"
What I'd do, is play some games with her.
Call it "The do you like game" or something. Tell her you're going to play a game...ask questions like "Do you like unicorns?" and tell her she has to answer YES with a big thumbs up and a nodding head if she does like the thing you're asking about. And if it's a thing she DOESN'T like, then she has to say NO and do a thumbs down and a big shake of the head.
When you play it, at first, give her a big list of things you know she likes....so as not to confuse her.
Then move on to things you know she doesn't and do a lot of those.
Tell her "If it's a thing you REALLY like then the YES has to be loud!" and the "No has to be loud if you REALLY don't like it"
That will make it more fun.
Do this and the physical actions and fun might help her to get used to it a bit more.
In day to day life, try prompting her... like this "Do you want salt on your eggs Mary? Yes or no?"