Write a letter to the principal suggesting the kind of teacher (caring, supportive, motivating, etc.) that you would like your stepdaughter to have next year. Sit down with that teacher as soon as school begins in the fall and set up a plan to support this girl in the areas she needs help.
Be aware that sometimes, even though teachers and parents know there is something wrong, learning differences don't show up until third, fourth, or even fifth grade. If your stepdaughter's problems continue, you may want to ask that she be re-tested at the end of next year.