Is prepping drinks by the dishwashing sink bad?

Writing this today from my chaotic job where no one, not even my fellow managers can seem to get a clue. So I work at a coffee bar in a hotel, it's a pretty small operation normally only one person works the coffee bar, while whoever works front desk can fill in if the barista needs to do something else. I'm in my 30s and I have over 5 professional years as a barista under my belt and have been making espresso drinks since my early 20s. I had to use the bathroom, so one of the front desk managers filled in, when I came back I saw her making a drink for a customer, but for some reason they took the espresso from the maker put the cup on the sink we use to wash dishes (on the flat part where you set dishes before putting them in the sink itself) then poured the steamed milk into the espresso. After I told them what they where doing was wrong, they get upset with me telling me "that (they) prefer to make drinks there," and that I shouldn't correct them because "(they) have a good handlers license." Needless to say I myself am pretty upset because even though they are front desk manager and also a coffee bar manager they should know that is against health department regulations. Am I overreacting though? Would anyone else get upset if they saw a coworker do what I just saw? I know my boss won't listen because they have a bout as much kitchen experience as a boomer who's never worked a kitchen before... Because that's exactly what my boss is. I feel like I am better than this job and should quit ASAP.