I made the same decision 7 years ago, for the same reason! :) First, you can use any curriculum, or mixed curricula that you desire. The requirements for Texas are found here: http://www.hslda.org/laws/analysis/Texas.pdf.
You will likely find that a gifted student will fly through the early curricula, and will find phonics-based reading very fulfilling (decoding is fun!). My oldest was in 2nd grade by the time she turned 5. Some subjects are easier, and she is still ahead in some more than others. The beauty of homeschool is that you don't have to hold her back where she wants to fly, and can still get in the things she doesn't like as much :).
There are several great used homeschool bookstores and resources online:
http://www.home-school-inc.com/ (planning and recording her work)
http://www.tea.state.tx.us/index3.aspx?id=3264&menu_i... (released TAKS tests she can take, and have scored online)
http://www.usedhomeschoolbooks.com
http://www.triviumpursuit.com/
http://www.amazon.com/
http://www.finders-keepers.net
http://www.workboxsystem.com/ (excellent system for setting up school... works GREAT, wish I'd found it sooner!)
http://www.cornerstonecurriculum.com/ (Math, Art, Science, History ... local homeschool dad created it; he used to be a public school administrator)
http://www.hometrainingtools.com (new science stuff, but still good prices)
http://www.homeeducatorsresource.com/ in Lewisville, my favorite brick and mortar store for browsing curricula, and they can answer any questions you have! They've been homeschooling for gobs of years!
I spend about 4 hours each day in instruction for my 3 (1-6 grade), but my youngest (5.5yo) spends about 1 1/2- 2 hours each day doing his work, mostly right next to me. At this age, the instruction usually takes longer than the seat work.
My MIL home taught her 6 children, several of whom were/are gifted, and her advice has held up well with my brightest children: Remember that s/he's only 5, and fine motor skills will be way behind his/her mental skills. So, handwriting takes a back seat to reading more often than not, and following a 1st (or 2nd!!) grade curriculum to the letter for a younger child is often a self-defeating project. They're really not ready for that much seat work. Also, many curricula are designed for private schools, and that requires more seat work than is usually necessary to get the point across, especially for a gifted student. Use your best judgement, even with the best curricula, and have her do only 1/2 the exercises on content she can demonstrably understand. Skip entire assignments, even! This was the hardest lesson for me to learn when my daughter was first beginning school!
Good luck, and feel free to PM me with any questions, concerns, or just moral support needed! :)