Forsaking Witchitude to become a Vampire

My witch is now married to a Vampire, she has been asked to forsake witchitude but it appears that nothing seems to happen,  I wish her to become a vampire changed by him, but since getting married the option to turn has gone.  I dont want anyone else to change her, yeah its only a game, but my Sims are always faithful to their partners despite the gossip that seems to appear from time to time!!!  So can you  help me.  I have come to a bit of a halt at the moment. 

Thanks