Apologize, apologize, apologize! Don’t make excuses (“I thought I was helping…”) Let her know you were wrong, speaking out of your own frustration, and ask her to forgive you.
Gaining competence will increase her confidence, so, instead of announcing good therapeutic ideas, ask her: “This sounded good to me, but you know yourself best; what do you think?”
One of those therapeutic ideas, which I found very helpful when I was researching ADHD on behalf of my son, was listening to (at the time) audio cassettes about ADHD. She may find them helpful- just globalizing, if not normalizing, difficulties that she thought were hers alone might help her immensely. Again, her decision.