I know it's scary to make a big decision like this. Look at the extremes, though. What's the best that could happen? The worst? Can you handle both those? You aren't investing a huge amount of money (like buying a new house and moving to a new school district) nor are you making a non-reversible decision. If it works, that's great! If not, then you do something else. After all, it is Kindergarten and lots of kids do Kindergarten twice (red-shirting) so you can always move her to a different Kindergarten or put her in the public Kindergarten in the fall.
I know it's easy for me to say. I made the decision for mine to skip 2nd grade and was very comfortable with it until this year (7th grade) when he's with kids in band who are 3 years older than he is, but he's happy with the skip and it has been good for him. I don't really regret it; I just wish sometimes he could have stayed "little" longer.
Good luck with your decision!
