I would look for a preschool that is mostly free play but has an ample supply of books, a science and nature table, as big and natural or garden like playground as possible and teachers who actually talk to the kids about stuff. If I could afford it though I would go for a nanny who would spend hours outside in the fresh air, take her to activities and play games and read a lot. I would also have a reasonably predictable flow to the day and week.