I taught my 9yo sister to SSH from my Arch Linux system to an Ubuntu system, she was amazed to see terminal and Firefox launching remotely. Next I taught her to murder and eat all the memory (I love Linux, as Batman, one should also know the weaknesses). Now she can rm rf / --no-preserve-root and the forkbomb. She's amazed at the power of one liners. Will be teaching her python as she grew fond of my Raspberry Pi zero w with blinkt and phat DAC, making rainbows and playing songs via mpg123.
I made her use play with Makey Makey when it first came out but it isn't as interesting. Drop your suggestions which could be good for her learning phase?