While I agree that no prep should be done for a test like that, I think that giving her a brochure explaining what types of questions and how to approach them would be very, very helpful.
For example, I would have never, never guessed that calculators are allowed, if it was not for above posts (mind you that I do not believe in calculators at this level, but that is totally different issue).
At this time we are not even familiar with the test format. Should she guess or will she be penalized for wrong answers? I think you get what I mean.

Interestingly, while we are on a subject of keeping kids informed. Yesterday while talking about one of the teachers< Ghost started ranting about how unfair she was last year during science. Kids were building wooden bridges, to be tested for which one was the strongest - could support most weight. Ghost was asking this teacher several times HOW the bridges are going to be tested, each time she replied that this should not be a concern of his (YOU DO NOT GIVE AN ANSWER LIKE THAT TO A GIFTED CHILD), and that he should just concentrate on building the strongest bridge possible. So his group decided, based on Ghost observations during science olympiad, that the test will consist of suspending weight at the middle of the bridge. They build a solid product and did it fast, at the end decorating it with some straw railing. To his surprise (more shock!), the test consisted of placing books on top ofthe bridge! Gues whose bridge was the first to collapse under pressure???
He was madly going about it last year at some point, I just ignored it and switched my listening off. Only found out the details yesterday.
So yes, I am all for keeping kids INFORMED.