I don't know your reasons but I am sure that you have put a lot of thought into this decision and I want to assure that it is not too late.
Check out HSLDA's (Home School Legal Defense Association) website for laws in your state.
There are a lot of different curriculums available and it will take some time to decide what fits best for your daughter and teaching style. If you don't want to finish out with her current texts you could switch to something like A Beka for the rest of the year (The basic textbooks are inexpensive, and don't need all of the extra materials that run the cost up.).
My absolute favorite curriculum is Sonlight. It is so much fun, and my kids love it! If you go to their website, you can find a ton of information. They also have a great forum where you can get great advice.
Regina