HK has great advice. It's hard to do, but try not to fixate on the number and instead, just expose her to many different things. She'll gravitate to those that interest her now. Some will stick, some won't, some will disappear as interests and then reappear.
We've found allowing nearly free reign at the library has worked very well over time. That said, yes, DS ran through all the Rainbow Fairy books and Captain Underpants (yuck) has been spotted at our home. He also has devoured plenty of nonfiction on everything from planets to robots to history. That sort of thing works itself out with our children.
