Hi, I agree with Trufin - your cat is trying to get your attention about something she is unhappy with.  It can be, as Trufin has said, that she dislikes either the type of litter or the cleanliness of it.  Some cats are super picky, some could care less.  I have tried switching from clumping litter to pine or newspaper litters in the past, and this is the response I get - a big "thumbs down".  It could be also your cat is shy or nervous - too open of an area or too much traffic walking by.  If you have more than one cat, they may not want to share.  More than one box may help, and make sure there is at least 2 inches deep of litter in the box.  

However,  if your kitty has been going in the box with no problems until recently and nothing about the litter has changed, you may want to consider a vet check.  Since she is a girl, cystitis is less of a possibility but can still happen (crystals in the urine).  Some females can get urinary tract infections also.  Some cats associate the burning sensation with the litter box - she is trying something else in an effort to relieve the discomfort, and to signal you that there is a problem.

A simple urine test at the vet may solve your problem.

Hope that helps!