How can you get your Sim to not be engaged to a dead Sim

You can talk to the ghost, if you happen to run into them in your house, but if you have the 'testingcheatsenabled true' (without quotes) cheat on, you can right click on the sim and select "add to active household"....or you can have this same cheat on and go to your mailbox, right click, then select "set career"..."science"..."mad scientist". then go to the science facility and restore your ghost. Keep in mind, you need the gravestone in your inventory. once you do this, you talk to the ghost, select "mean"... then "ask just to be friends". This should work. Hope this helped.