i used to have to same problemwith my little brother , heres what i did...
1)create user accounts on the cpu , and pw protect mine
2)create a user account for everyone else , with a pw
3) run the bot on your account , log out
then she can still do what ever she has to do , your bot still runs , and she never knows , but i don't know how you could keep her form shutting down the computer though......heheh, maybe if you just smacked her a couple of times , told her to just stay off