Whether or not your daughter is retained, you've lined up a great deal of support for next year. The medication coupled with the resource help will make a big difference in helping your daughter. You don't mention how long she has been on Adderall, but children typically make great progress in writing once they begin taking this medication.
Talk with the school counselor. Ask if there are any developmental screening tests (such as the Gesell School Readiness Test) available to help you with this decision. The counselor may also be able to give your daughter some individual time or include her in a small group on self-esteem either this spring or in the fall.
Your daughter will take her cue for accepting the retention from you. If she sees that you believe another year in her current grade is the best thing for her, she will believe that as well. If she feels that you don't believe this, she will worry that something is wrong.