Greetings ! Welcome to the site. I am sorry to learn about your daughter s condition and I empathize with her. I agree with you that she has been over-loaded with psychostimulant drugs such as vyvanse and Adderall and that too at their optimal doses. So it is quite possible that the insomnia she is dealing with is a side effect of these two drugs, so I reckon instead of starting her on Seroquel which is mainly an anti psychotic drug with additional sedative action and which may come with it s own set of side effects, better ploy to handle her insomnia / lack of sleep will be to reduce the dose of Adderall to half of what she is currently taking or else choose a pure sedative/ hypnotic drug like zolpidem at a dose of 5-10 mg at bedtime, starting at lower dose first and this shall be taken on PRN basis that is as and when required basis to help her sleep. In fact a combination of dose reduction of Adderall to half of it s current dose and introduction of zolpidem at night at low dose thereby bypassing the need for an antipsychotic like Seroquel shall be the most appropriate and plausible solution for her insomnia. I hope this helps. Wish you and your daughter all the best. Take care. Regards..