Stop syncing to a computer I no longer have access to.

Most of my Dropbox files are synced to my home computer.  I've recently ended a personal relationship with which some of my Dropbox Folders were Selectively Synced to that person's computer.  I can't seem to figure out from my Dropbox Account how and where to go to stop their computer from having access to those selectively synced folders from their computer since I no longer have access to uninstall the desktop App/account on their laptop.  Any advice would be helpful.