I don't think you have to worry about pushing a kid under that age of 5. There are a few kids who get super cranky if not pushed, and those you have to push. If you follow your daughter's interests and delight in 'geeking out' together you will provide all the 'right stimulation' she needs.
What you have to worry about is 'teaching' a child that
a) school is for being bored/acting dumbed down/causing trouble
or
b) other kids are not 'real' but instead incomprehensible automatons without souls
Montessori's seem to be either 'heaven or hell' for unusually gifted kids. Some are run by wise observers who are ready to take an unusual path with an unusual kid. Some are run by insecure folks who automatically resort to 'the book says a child MUST be good at X before we can give her the Y materials' or 'all kids who are X age can function between these limits.'
The best is to find a place where the kids seem to be appreciated for who they are, and there seem to be one or two kids who you think your kid would find 'really cool.'
Preschools can be a great opportunity to expand your social network as well as good placed for your child to learn to be in a group. The vast majority of kids can be put in a classroom with agemates and learn valuable social skills at age 3, but if the main reason to put an unusually gifted kid into a classroom setting is to learn to get along with peer, make sure that there are peer in that room.
Lately we act like Preschool is a nescessity. I'm in favor of Preschool if it's important for your family to get some time off, or if there are opportunities there for the individual child, but I don't think it should be a knee-jerk decision.
Sigh,
Grinity
