Does the Necrocall spell even work?

It must be a glitch because even after moving several children out of the house and Bella herself dying the spellcaster could not get the two urns of Alexander or Cassandra to do anything.  There must be a time limit of how long they had been dead.  Meanwhile even without magic your could click on Bella's urn and select "strengthen ties to the physical world" and she came out as a ghost and then the spellcaster coudl use the Dedeadify spell on her and voila.  She was back, albeit as an Elder so likely she'll die again at some point.