Every snake I have will hiss, huff, and puff when you first disturb them in their cage. Only my tree python ever bites. The rest have never done anything more. I Don't think a hiss should be considered aggression but more of the only way they can communicate. I Think of them as saying here I am. A hiss is like a dog barking in my book.
I also think we don't give our snakes enough credit as far as how smart they are. My ball was in her hide one time and I reached down to see which one she was in to feed her. My fingers went across the door and just under the edge to Tip it up to see inside. She did nothing. But as soon as I brought the mouse close to the hide to lure her out lighting struck and the mouse disappeared into the hide. I was really impressed. I'm not trying to say that they should never strike us but I do think they are smarter than we realize. I'm sure the others are right and yours was still in feed mode and thought she detected another feeder but she didn't bite or strike you so I think she realizes your not food. This is just my crazy idea nothing more. Maybe my ball is just super smart. LOL!