I went through the same. I am so proud of the calm effort my daughter made convincing me to let her try Vyvanse. I’m not so proud of myself for not listening and being so closed minded for so long.
My advice. Support her decision. Read the Vyvanse reviews, you will hear all sides. But note that the product gets 4 out of 5 stars for good reason. Before your daughter starts get her review the testimonials so when she has a crash or side effect she and you are aware and anticipate and agree on a strategy should a side effect occur,then go for it.
Please don’t hold your daughter back. Everyday is precious. Let her excel.