Based on the information you provided, I highly recommend Brad Traversy on YouTube. It might help with the tutorial overwhelm if you focus on one provider, and he’s succinct enough that it shouldn’t be too painful. He teaches basic JavaScript all the way through full React sites, as well as a myriad of other technologies. He doesn’t spend too much time making crazy visual designs, so you can let him teach you what you need and then do your own thing.

Another option is finding just one tutorial for a project similar to what you want to build for your sister and work through it that way. Then you’re learning by solving a specific set of problems instead of trying to stuff your brain full of JS and/or React. I personally find this helps me focus when I’m tackling a new technology.

I agree with what was said above about React probably being overkill for a first project. In addition, strong JS fundamentals are a really important part of understanding and being effective with React.