It's never happened in my incubator...or in my hands, but there have been a couple that exploded when they hit the ground when I was disposing of them. That is close enough for me!!
I wish for this kids sake her egg was going to hatch, but at this point in time I'd say it's highly unlikely...
Are you sure that the wiggling that you're seeing isn't the box moving and causing the egg to move when you look in the window? It doesn't take much movement of the bator for the egg to move a little.