Or, if the water line froze before the water heater, she could have ran the water out of the heater (and it could not refill properly at the time due to the frozen feed line) and it ran dry which can cause all kinds of issues for an electric water heater, which could cause it to flip the breaker. Or as others have stated, the water heater has a bad element, from sediment causing similar behavior and then a line froze.
Nah...If the feed was frozen, then there was little or no pressure to force the water out of the tank. It'd be just like if you shut the valve off at the street. If the tank were elevated, you might get gravity to syphon it out but you'd likely have to have a way for air to get in or you'd probably not be able to maintain a stream.