Having grown up with 2 older sisters I have learnt that you never let a girl no matter what the age walk away angry and thinking that they need to get back at you. What you should have said was something like "I will show you, but only if you prove to me that your old enough by doing X", and making X an impossible task of some kind. That would have distracted her with something else and she probably would have forgotten about it some time later if she was going to your granparents anyway.

Either that or you shouldn't leave your laptop just out in the open where little hands can snatch it.

Hope you passworded your profile at least!

See, this is why you shouldn't keep naked pictures of yourself on your electronic devices. Make sure to delete them as soon as you get your laptop back.

And about the paper...I'm so sorry. Always make sure you keep a back-up or two.