Re: Caterer that shows up isn't Sim who was Hired
It seems that the logic for what sims appear in the "Hire Specific Caterer" menu and what sims are able to fill the actual role is different. It makes sense for planning parties for example, where by the time the party would take place the NPC that was hired is no longer able to fill the role (otherwise engaged, dead, etc).
In this particular case, i think the issue is Vivian Lewis does not have at least level 5 in Cooking in order to receive the Caterer role. So she is replaced.
Vivian Lewis has a default Cooking level of 4. Indeed she wouldn't show up to the house when I hired her as a caterer. Other sims DID show up (Milla Munch, Ava Harjo, etc).
I increased her cooking level to 5 and she came when hired as a caterer.