Who is in the wrong with this situation?

My friend and I were in Hallmark trying to find a card for a friend, nd they were the singing ones that run on the battery. We were opening them trying to decide which one fit better, when out of corner of my eye I saw the cashier standing there. She then proceeded to tell us that she didn't like it when we opened the cards like we did, becuse we were wasting the battery. I told her that it helps so we can actually find a card we like, nd she didn't like what I said. I responded by saying we'll find buisness elsewhere, nd left. She said good. It's such a silly problem, but it got me angry. Who's in the wrong here?