On the top of my mind...
Sarah Petrausch
She was the outstanding player of the German junior NT that won WCH 2009, I think she was best scorer of the tournament and the only reason she didn't win MVP was that Brenda Castillo played in the same tournament. She made her senior NT debut in ECH the same year but she never managed to show a decent performance later on and was a big disappointment also in the league.