The good news is, you've got a lot of time.
At this point, I'd start thinking about where your kid is now in terms of what she needs to know for K... letters, numbers, shapes, colors, letter sounds, writing name, coloring within the lines, etc. If she's already where she needs to be, or very soon will be, then it is an appropriate time to begin asking the same question I kept asking my DW at the stage you're in right now, "What are we going to do with her when it's time for her to go to school?"
Definitely, start reading all the materials you can about the nature of giftedness, which will help you understand your DD better.
And finally, learn all you can about your available options. What are your state's policies regarding gifted education? What is the public school district's policy on early admission to pre-k/K? What charter or private options are available in your area?
