I didn't do any preparation for the ACT and got a good enough score, but felt like I could have done much much better with a little bit of prep.

So when I took the GRE I determined to do my best by buying prep books and taking a prep test every week. It paid off.

I can't think of a single other approach that will yield as good of results. It will help with her pacing (I had the same issues), it will reveal deficiencies that need to be corrected, and it will help the real test feel like a walk in the park.

Side note, I'm not one that recognizes direct answers to prayer but I gained a strong testimony of "treasuring up in your mind" when it comes to truly important tests. I didn't receive answers to questions, but I was comforted and reminded that I knew how to answer questions that I felt like I didn't.