LAN minecraft server?

If you're just doing a LAN in your own household then you should just be able to start a game and then open the menu and click "Open to LAN"

Then your sister should be able to go to "Multiplayer" from the main menu and look for LAN games.

If that isn't working, you might have permissions issues regarding your network. Windows might not be letting you open your Minecraft up to others over the network. Though I can't say offhand how to allow others access via your home network.