My wife does that all the time! The real problem is that she seems to think I'm a lot more complicated than I actually am, so she reads into what I'm asking thinking that I'm asking a much more complex question than I am, when really I'm asking a very basic question and looking for a very basic, short answer.
I just wait until she's done and then repeat the question, which usually results in getting the short answer I was looking for in the first place. She just has so many words she needs to get out of her system before she can get the real answer out, I guess.
We're perfect for each other, though. In social situations she takes care of all the conversation, and I can just stand there drinking my beer and occasionally throw in a word or two to clarify or emphasize certain things. It works out great!