In my experience the main reason women don't end up in STEM fields is simply because they don't understand what steps to take or (more often) they haven't been

In my experience the main reason women don't end up in STEM fields is simply because they don't understand what steps to take or (more often) they haven't been exposed to the ideas at all. Fundamentally (in the US at least) they're simply not shown compilers, CAD, electronics etc as high school students. The few women I met in college who went into engineering and CS did it because someone went out of their way to show them these things or their high school had a special elective program that had them play with the ideas. If I where you I would show them some simple neat idea that can lead to more complex conversations (Cellular automata is one someone showed me and that ended up being the main component of my first non trivial program I wrote as a teenager. I'm not a woman but I'd imagine this is a human thing and not gender specific.) IMO too many kids are "held by kid gloves" and aren't given the languages and tools to participate in adult conversations so they can see some of the more amazing things in the world (again, for me this was the C programming language, for many other people it was math) If you can give them something interesting (physical or not) to take home and study on their own you'll probably change their lives.