I’m so sorry to hear about what happened with your brother in law.I can completely understand your hesitation.
I would find a Psychiatrist that specialises in ADD to talk to first. Hopefully they can explain how the medication works to put your mind at rest. Antidepressants are much scarier with their side effects than ADD meds. I’ve had depression and anxiety since early teens, and it was an unpleasant experience finding out which antidepressant medications didn’t worsen my symptoms. I was also misdiagnosed with bipolar in my mid twenties, and the meds I tried to tried for that were also absolutely awful and crippling for my mental health.
It’s only been quite recent that I have been diagnosed with ADHD, and the change for me since being on ADHD has been only positive. The doctors will start her on a very low dose and will make sure she doesn’t experience any negative side effects before increasing it. She can also start on a short acting formulation that will only work for four hours, so if she does experience any side effects, it won’t take long to wear off.
I can understand it must feel terrifying starting her on a medication given your previous experience with your brother in law. I believe that the ADHD meds have been very well researched over the last 30 years, and the drugs that are on the market are mostly variations of the same two molecules.
I hope this helps. It might also be helpful to hear in mind that many studies have proven that people with ADD/ADHD who are treating it do much better in life than people with ADD/ADHD who are not treating it. As a person who was diagnosed later in life, this is something I relate to very well 🙂.