I may be in the minority, but I wouldn't do any further prep beyond what came from ACT for two reasons:
1) you may want to get an idea of what she can do without prep to get the best idea of what placement she needs right now;
2) I wouldn't want to play into her worries about it being a big deal.
Dd12 also stressed on the day of the test when she took it at age 9. She came out crying & didn't do nearly as well as she could have on reading in particular b/c she was worried that she didn't know everything and kept leaving the test to go to the bathroom during reading b/c she was crying... She didn't come close to finishing from what she said.
I'm not necessarily advocating that kind of stress for your kid but, in our instance, it is part of who she is. She wasn't at all used to anything being a challenge at that point. It scared her, but it was really good for her to learn how to deal with anxiety and things that were hard b/c she didn't have a lot of experience doing so at that point. It also helped that her scores weren't nearly as bad as she feared. Both science and english met the DYS criterion, actually. It helped her see that her overblown fears were exactly that.
After a few years of taking tests like this (she's done the SAT and ACT since then), her response is seriously better. She goes in much calmer and comes out feeling okay about not having finished or having to cobble together a conclusion for an essay in a few minutes, etc. That's what we wanted: a child who could work through her fears of inadequacy, learn to cope with challenge, and keep functioning.
I don't think that prepping her so that it wasn't scary would have helped for my dd. It was facing the fear and working through it that helped her.
