This example is not the best......................
You engage someone off of FB to be a bartender at a party to be held in your home "that night". You don't know that person, no backround check, not a licenced profession (AFAIK) in the state. Just a "person" who responds to an add. ( for all you know it's her way to go to a party, have a few drinks,go home with a client

D) and get paid. Or maybe front on a home invasion w/ a few "friends"). Pretty stupid IMHO.
She shows up open carrying.You have no idea of her training/experience. But you now know she is carrying....... so you knowingly engaged her services her act as a bartender............ armed!
As the homeowner/party thrower I would not want my catering staff openly armed...... it not the impression I want to give at a party I'm throwing.
As the homeowner who has employed her you in all likelihood will have some or full legal liability for her actions..... both in the amount of alcohol she serves and what she does with the gun.
If she shoots someone who attacks her or a bystander; or serves someone to many drinks and they kill themselves or someone else on the way home.You as the homeowner/party thrower may be liable or at least face a civil suit.
None of which has anything to do with her right to carry IMHO..... here's the job here are my rules.
Orkin man ....... employee of another company, with ID,driving an Orkin truck...he's covered by Company policy.... CC I should never know, Open carry I'd call the company and confirm his ID and company policy...... then make the call based on my comfort level.
FYI: I tend to CC when I have "unknown" contractors in my home....................