One of the things that encouraged my programming early on was modifying BASIC programs to do different things - all the hard work was done and I could experimen

One of the things that encouraged my programming early on was modifying BASIC programs to do different things - all the hard work was done and I could experiment and learn how the various functions worked, sometimes even develop some new nifty things. You might try finding a good language with some usable/interesting example source code that she can fiddle with to start. Possibly Python with pygame or Processing might be a couple good start. Besides the modding she might get interested in see how X was done and then she can google it and learn the functions she sees in action.