Sometimes when I ride in areas with a lot of debris on the road (leaves, twigs, etc) I can hear stuff ping my spokes.
I'm guessing she ran over something that hooked inwards towards her wheel (small tree branch?) and sheared the spokes and fork.
Bad luck.
Oh and about carbon forks: I was stupid enough to get a hacksaw stuck in my front wheels while riding along. Don't ask! Broke a spoke and scared the hell out of me but only rubbed the paint on my forks. Carbon is pretty tough.