Oh my word.
First, agreed with everyone else about correct boundaries on who sets up a cake. But you've learned.
Next, I'm sorry but grow a backbone or finish cakes earlier. If they show up 1 hour early, you say "um, you're one hour early, go away." I can imagine the kind of pressure you were under trying to get a cake finished while the customer is waiting for you. That would lead to disaster in my bakery as well, as I don't like having any kind of audience.
If you don't want to tell people to go away, then at least finish cakes the day before so they have time to chill properly and then they have less chance of disaster. Then if Aunt Flo shows up all clueless you have a much better chance of thinking on your toes.
My heart goes out to you and I pray the fallout is short lived!