Maybe she does, but the rest of us use the bulk of it. I intend to add more to this page, but I'll start with a quote from Carl Sagan, from his book 'The Dragons of Eden':

"There is a popular contention that half or more of the brain is unused. From an evolutionary point of view this would be quite extraordinary: why should it have evolved if it had no function? but actually the statement is made on very little evidence. Again, it is deduced from the finding that many lesions of the brain, generally of the cerebral cortex, have no apparent effect on behavior. This view does not take into account (1) the possibility of redundant function; and (2) the fact that some human behavior is subtly. For example, lesions in the right hemisphere of the cerebral cortex may lead to impairments in thought and action, but in the nonverbal realm, which is, by definition, difficult for the patient or the physician to describe."

Carl Sagan in the Dragons of Eden, page 31

Here, look at this:
http://www.urbanlegends.com/science/10_percent_of_brain.html
CSICOP's take on the whole 10% of brain thing