Welcome!
Both of the states you name do not require or recommend formal testing of the WPPSI/WISC/SB variety until at least second or third grade for GT identification through the public schools. Multiple measures usually include portfolios documenting work at least one year above age-locked grade level; I would agree with Portia that a portfolio is likely to be more productive, especially since the gold standard IQ tests should not be administered more frequently than every 24 months, so if you have her tested within a certain distance in time from when the district decides to test, you may have burned the administration opportunity on premature testing.
In any case, differentiation is more useful if it is based on where the student actually is performing at the moment of differentiation, rather than projections of where the student will be performing. And nearly all schools use probes for reading and math achievement at least three times a year, and often monthly for the primary grades (K-2). Teachers will have many opportunities to document an incoming student's achievement on, below, or above grade-level expectations. The data will be there.
Now if early entry or grade-skipping is your thought, you will need to inquire at your actual LEA (public school district) about policies and decision-making processes for early admits and grade acceleration. For example, one of the major municipalities you name does not admit early under any circumstances whatsoever. However, they will enter older five-year-olds directly to first grade if they have already completed an accredited full day kindergarten (presumably private, or transferred from another district) program. So in that district, if you wanted to get a grade skip next year, you could do so if your child had a birthday no later than Feb 1, 2015, and you would also have to transfer your child into a NAEYC full day kindy this school year.
Other than when entering kindergarten and first grade, nearly all public schools will allow a student to transfer in from a private school based on their last grade completed. But that just pushes this question to a private school (and costs extra tuition).
On a totally different note, it may be well to consider what is in the best interests of your child's overall development. Academic development is one thing, but there's plenty of time for that. The preschool and kindergarten (and even first grade) years are principally about soft skills. It may be that your child is equally advanced in many of those areas (social skills, emotional regulation, fine motor skills, attention span, etc.), and a global acceleration would be appropriate. Or it may be that some skills are far ahead, some are delayed, and/or some are right on age-level (aka, asynchrony). In this very common situation, placement decisions will require weighing the need for challenge, peers, or remediation in different dimensions, and will inevitably involve tradeoffs. In any case, wherever she is today, she will be in a very different place a year from now, or even six months from now, just because of the nature of early childhood development.
Also, whatever decisions are made won't be nearly as immutable as you may currently feel they might be! Observe her, collect any interesting portfolio items as they are produced, and enjoy her. It is highly likely that she will signal when the school environment becomes unsuitable, and you, as an attentive and caring parent, will start to feel that something is off. Pay attention to those subtle cues, and investigate when they emerge, but don't feel like you have to forestall any moment of educational misfit before it occurs. Permanent harm is unlikely to ensue from temporary mismatches.
