I think that if she is having fun, it is fine. Kids are ready for different things at different ages, and different kids enjoy different types of activities. I've done a ton of research and can't find any evidence that early academics help a child at all. There is evidence that pushing a child can be damaging, but if you aren't pushing but rather just enjoying time together, it is OK.
One things that is important to me is that my kids learn to hold the pencil correctly rather than getting into bad habits that will have to be fixed later, so my 3 year old doesn't do the kind of tracing letters and numbers that shows up so often in early workbooks because she can't hold a pencil correctly.
A book we love at our house is "Sandbox Scientist: Real Science Activities for Young Children" by Ross. It has directions for science kits that you put together and then your child play with as they see fit. Many of the ideas are very simple and easy to put together, and my kids LOVE everything we've done from this book.
There are tons of arts and crafts ideas on the WEB. Our fav is
http://www.theideabox.com/
Here is a nice article on homeschooling for preschool.
http://eho.org/features/preschoo.htm
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