I could never make my mind up on this one. I suppose, in the end, only she knows what really happened. I'd like to think she was innocent.
I could understand if she did lose her temper and shake that little boy though - she was 19, with no experience, far away from home, completely isolated, and working incredibly long hours with little or no support looking after two small children (Matthew was 8 months and his brother was 2) - for a pittance. It's a hell of a lot of responsibility and pressure to put on a young girl's shoulders. I'll never understand why two well off and well educated people would entrust their children to a teenager with no experience.