I don't know the reason she would do this but I like the suggestions of getting books for her. The other thing I wanted to mention is to not get angry with her. Sometimes these "little issues" are caused by something else. So, with that said, encourage her with a 'pamphlet' or little book made for girls and ask her questions like "Which girl are you most like?" or "Do you like to feel clean too?"
The one thing I wanted to mention to you is do a little reward chart for her. Every time she cleans herself properly, morning and evening, she gets a star or a sticker. 5 stickers, she gets a little prize. I do this with my kids and I use stuff from the dollar store. My son gets pads and pens and little matchbox cars, etc. It will be fun for her and all around a win-win.
You may feel a little pinch in your pocketbook but now, the thing I wanted my son to do, he does now every day - no hassles - and he has kind of forgotten about the "prize bin."