It's not funny, it's sad. Suppose you'd been lying there, dead; her response, "oops, my bad", sort of doesn't adequately convey a sense of remorse. I'd want that person to say, "Damn! That's the dumbest thing I've ever done! I'm sorry I assaulted you, please forgive me! I've learned my lesson, and from now on, I'll always point the muzzle in the safest possible direction."
"My bad"; really. I mean, like, really!
My first thought (remember that to the man with a hammer, every problem looks like a nail) was that what that person did was brandishing a firearm, assault with a deadly weapon, simple assault both as a crime and as a tort. I settle cases like that for damages in the neighborhood of ten thousand dollars. I'd love to have a defendant come in one day and say to a jury, "Gee, my bad."