I don't believe for a second that gun went off without either being dropped or her accidentally pulling the trigger. This is a very rare event, but Remington 700s do sometimes fail this way. The striker can fall when the safety is released.
I have owned one for years, excellent rifle, excellent value, too. Mine has never malfunctioned in this way, and 9999 out of 10,000 never will, but it can happen.
But it (the safety) can fail.
Which is why you, and everyone who posted before you, never point a loaded firearm at something you don't want to shoot.
Not to belabor the point...well, yes, to belabor the point...Don't aim at what you don't want to shoot!