She is the champion of the Sinnoh region. You'll need to beat her when you get to her. In certain places, she'll come see you to give you some things to help unlock certain Routes and towns. In Platinum she'll give you an Pokemon Egg.
The Pokemon Champion is Cynthia
In Pokemon Diamond (and Pearl), Cynthia's first Pokemon is a Spiritomb. Her other 5 Pokemon are Garchomp, Gastrodon, Roserade, Milotic, and Lucario.
Cynthia
She stays in the Pokemon League.
Cynthia.
The champion in the Elite Four.
You have to get the SecretPotion from Cynthia.
Cynthia the Pokemon league champion has one
SPRITOMB you can see it in the elite four.Champion Cynthia has it.It is her first pokemon.
The champion is Pokemon Diamond, Pearl and Platinum, is Cynthia. She has various Pokemon-types. She is the Sinnoh Champion. Her Pokemon are Spiritomb, Lucario, Togekiss, Milotic, Garchomp and Roserade. In Platinum, Cynthia has a Togekiss. In Diamond and Pearl, she has a Gastrodon.
Cynthia is not in a contest so who told you she was in one?
Beat Cynthia after Elite Four