Hi katdemonninja,
You can have your Sim start the science career and early enough, she should get the "Restore a loved ones remains" opportunity which should allow to make her husband come back as a ghost.
- Put the remains/tombstone/urn in your inventory and go to Town View. Click on the Science lab and select the option to restore the remains and head to the Science lab.
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Your loved one will be restored to a ghost and you will be able to do anything and everything with your ghost Sim that you can with your living Sim. Make both Sims go home.
