A slumber party and a surprise party put together. You would first invite the person over and have a picnic and ask her if she would like to sleepover and if she says yes tell her to get her stuff together and meet them at your house in an hour and in that period of time put up all decorations and get everything together. then when she comes surprise her and she will love it and remember to include karaoke and presents since she is moving and also do make overs and do each others nails talk and wish her the best in her new house and new state and you can also play truth or dare that is what most girls around the ages 10-13 love to play it is the "in thing". And remember to have the party when it is nice out so you can have a picnic and if you have a deck in your back yard it would be so cool to decorate the deck and dance to the karaoke on the space left on the deck.