Hi M.,
I'm really old school on these tests, since I took them in the Sixties and did extremely well with no preparation except what the Educational Testing Service mailed us. That said, if your daughter is very anxious over tests, I recommend that she make sure she does all her homework and understands it. The other commenters have given you suggestions on books to read and websites--go to the library and get out some of the books and if she likes one best, maybe you could buy it. If your high school offers Latin, enroll her in Latin--even a little will help immensely in the vocabulary sections. Reading the introduction in a good dictionary might be helpful as it usually goes over word derivation. She should read one good book a week this summer to help her vocabulary and reading skills--Harry Potter is great, also Jane Austen, Shakespeare's plays, Pilgrim's Progress (if she knows anything about literature, she'll find out how many sayings come from Pilgrim's Progress!), the Diary of Anne Frank, the Iliad and the Odyssey, Greek and Roman mythology, etc. This kind of background should increase her knowledge base and vocabulary and the experience of the kinds of testing, and may relieve her test anxiety somewhat.
This being said, a lot of schools don't require these kinds of tests any more, so her scores may not be so critical. Also, she can always retake the tests.
I hope she does well.
E.