My guess?? She left it strung, in the sun...??
Old Bears, can give up the ghost at any time, but this appears to be a new bow. (quiver bushings)
Also, it's sunny, and she's wearing a tank top. It appears to be warm out.
Years ago, at the White Mountain Traditional Rendezvous in New Hampshire, I saw the same thing happen.
A guy had a (few years old) custom Robertson Stickbow lower limb fold on him.
He had left the bow strung, and laying on a picnic table, in the shade under the pavillion.
In the coarse of an hour or two, the sun had moved and exposed the lower limb to the sun.
This created a temperature imbalance between the two limbs, and to not draw equally, causing the collapse.
At least that's how it was explained to us, by a vending bowyer there....
I'm glad she wasn't hurt too!!