once you mark a household as played (by playing it, even if just for a moment) the sims in that household lose any service jobs that they might have had. They technically aren't even supposed to keep the job after moving into a home, but MCCC allows this to happen.
To get that specific butler back is a bit of effort. You'll need to enter her household and use the following cheats on her:
Butler: traits.equip_trait isButler
careers.add_career Butler
and furthermore she needs the following set of skills (but since she was a butler before, she probably already has the appropriate skill levels):
Handinees at at least 2
Charisma at at least 2
Gardening at at least 2
Gourmet Cooking at at least 2
Cooking at at least 5
After you use the cheats and ensure her skills meet the requirements, exit the house, mark the household as unplayed, delete the household containing the butler that replaced her and hope for the best. If she does not appear as the new butler, you will simply have to keep firing, deleting, and rehiring butlers until she does.
