thanks for asking Mominsac -
The SAT is fine for gifted 12 year olds to take. The test is long, but she can skip the writing portion if you think that will help her not run out of steam.
If you are taking the tests as a diagnostic 'above level test' to get an idea of what her LOG - level of giftedness, then the preperation should be
1) a few sample questions so she knows the format
2) the idea that guessing subtracts points, so wild guessing is a bad idea, but if one answer can be confidently ruled out, a guess is worth taking
3) that this test is developed to be super hard for HS kids, so don't be sad if there are lots of questions that she can't answer. The point is only to compare her to other bright kids who are 12 years old to help make educational decisions and perhaps get to go to cool activities and summer camp.
Actually, there might be a few instances where more prep than that is nescessary, but it doesn't sound like those apply. I know I felt nervous sending my son in with all those big kids, and I even drove to the next community so he wouldn't have to be with kids he knew. But as for the nervousness about sending her in to take a test she will find difficult - Celebrate that she can have her first experience like this in supportive environment!
She really can not lose.
Grinity