You think she walks around with shotgun shells in her pocket?
I get the feeling that a lot of people here don't really understand the difference between a double barreled shot gun and a pump action shotgun and why, when Biden said to fire BOTH barrels, he is being derided.
Just for the record. A double barreled shotgun is the type that has two barrels that are either side by side or one above the other. It can only hold two rounds of ammunition and has no provisions for more without a special (and optional, and not all that common) bandolier that wraps around the stock (the wooden thingy that you put up against your shoulder). To reload it one must first open the weapon up, remove the spent shell casings, insert two more shells into the weapon and close it back up. This takes some time and in order to be proficient at it requires practice by the user.
A pump action shotgun (a far more common type of shotgun for the reasons that you will see below) has one barrel with a spring loaded tube below it that can hold up to 5 rounds in it (plus one in the chamber if the user so wishes). It also has a sliding handle (the "Pump") that can eject a shell (spent or otherwise) from the chamber when you slide it one way and then load a new shell from the tube when you slide it back into its original position. A person who has never fired such a weapon before can easily reload the weapon on their first try. In addition there is the option of (when the tube is empty) performing a quick (or as it's normally called a combat) load by slapping a round into the chamber through the same port where an expended shell is usually ejected. This however takes some practice by the user to become proficient at.
When you fire BOTH barrels of a double barreled shotgun you are essentially defenseless for some period of time as you need to reload (a process which can take as little as 5 seconds or much longer depending upon the skill level of the user and their proximity to the proper ammunition. For a pump action shotgun if you for some stupid reason fire two rounds as warning shots (unlikely as one would be more than enough) you should still have at least 3 more rounds in the weapon.
What Biden was suggesting was to render oneself defenseless while simultaneously potentially endangering innocent people and more than likely breaking a local law or ordinance while doing so. This is why he and his suggestion is being laughed at.
Thus ends my pointless (for most people) lesson of the day.