I think that if she clearly qualified for the program, you don't need to prep her. The fact that she is a 2nd grader in a mix of 2nd and 3rd graders would indicate that. About a decade ago, my oldest DS was put in a pilot program where the 2nd graders were doing the 3rd grade math curriculum with enrichment. It was no problem for him or many others who were clearly qualified. Unfortunately, it was too small a group and I think they added some students to make the class a bit larger and those were the students who struggled a bit. For some reason, by 3rd grade, a lot more bright kids can handle math curriculum a grade up.
However, if it would make you feel better and your DD is not opposed to it, you can prep on the 2nd grade curriculum over the summer. I would look up the actual curriculum objectives for your district to see if your DD has any gaps.
