ghost computer in shared section of finder

yesterday my parent's macbook randomly showed up in the shared section of the finder sidebar, but that computer is in a completely different city! and its been several weeks since i last connected to her system, so i don't know why it would pop up all of the sudden now.

failing that my mom is secretly trailing me to work to make sure my hair is combed neatly or something, any ideas why this would be happening, and how get rid of it?

changing networks (work > apartment) doesn't seem to help, nor does rebooting the computer.