Just like Minecraft, Kerbal can get a little overwhelming and have a steep learning curve. Thankfully it has a strong community, again, just like Minecraft.
Scott Manley makes a great series of videos that will give her great ideas, starting with this one: http://www.youtube.com/watch?v=tgPr4q5tj-Q
Here's another series that is more linear in its knowledge progression: http://www.youtube.com/playlist?list=PLO-JFyNTqjIljuPwaHkGZpMOLTtfCuIYg
I will also recommend Google SketchUp, which is free. The learning curve is minimal, the cost is right - free! - and there is a bunch of prebuilt components she can download to play around with.
That's some pretty awesome minecrafting. Not to take this too off topic but she should check out the server uncovery.me (type that in for server address and in a browser for their website). She'll need to use their website to gain access/get building rights. It's a hassle since you need to pass a simple aptitude test which screens out idiots, the lots are protected so nobody can wreck up your stuff, and cursing isn't allowed so you won't have to worry about a minor playing. There are some amazing buildings there to give her some inspiration, too.
Edit: I tried to hotlink but I can't since the uncovery mobile site is blog-only.
Double edit- just like to mention the new subforum "simulation central" is for all games, not just racing ones. Although it is mostly racing, because racecar.
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