When I was working housekeeping in a hotel there was one day we were short staffed and already behind but I had to go bus tables in the restaurant because they were behind too. When I got there there was no managers around so I just got to work because I had shit to do. I had everything cleaned up and was standing there waiting for manager to come around since I still hadn't seen one. Well one came by and saw me looking bored so she said " oh Oyster, do you even know what you are doing here ?" In the most patronizing voice I have ever heard before. So naturally I stared her right in the eye and said I already did everything in a very unamused way.

So if she's anything like that manager, screw her but chances are she's genuinely trying to be helpful. In that situation I would probably just try being light hearted and maybe make a joke in order to balance the annoyed "ya I already did that"'s. That's pretty general advice but I also know very little about your situation so anything more specific would just be me projecting my own experiences onto yours. And clearly my own experiences have been... interesting.