If you're going to prank someone, you might want to reconsider choosing a person who is just trying to make a living and get through their shift. This employee clearly was already having a rough day and when two dudes rolled up in a truck with an airhorn, she decided enough was enough.
As someone who has worked multiple food service jobs to make ends meet, I totally feel this girl's frustration. I just hope she doesn't get into too much trouble. A little soda in the lap never hurt anyone...just their pride.