How do I help low functioning mother invest?

Long story short, my mother (50F) has been dealing with a lot of mental health issues over the last 15-ish years. She used to be super capable, spoke 2.5 languages, held multiple jobs, etc., but when she stopped working, a lot of that faded. She started experiencing paranoia, and social media didn't help much with that.

The last 6 months have been much better. I was able to help her get a decent job (call center, not amazing, but she used to do the same kind of thing working at BP; the idea is to get her back to that same level of functionality). She seems to like it, especially considering she hasn't quit after 2 weeks.

We're not poor, not rich either. My father focuses a lot on work and is frankly done with dealing with her mental health struggles 24/7, not entirely, it's just not something he wants to manage constantly, which is fair. Her getting this job helps a lot with that dynamic. He's a contractor, so he doesn't have benefits like a 401k, etc. I (18m) have my own business that I keep most of the cash in to grow it through sales and marketing, so no personal investments yet on my end.

Like I said, she's not all the way there mentally, and she has talked about investing (Apple, Google, etc.). I know for certain that picking individual stocks is usually not the best idea. What positive investments can I help her make that are extremely safe, and what brokers or methods should she use to purchase stocks, ETFs, etc.?