In all games, Whitney is a small young girl with pink hair and pale skin, and it can be assumed by her size and development that Whitney is in her young child ages to her mid-teens.
Whitney wears a white and red t-shirt, as well as very short white shorts, ending at the top of her thighs. She also wears red sneakers and black socks.
Whitney's appearance slightly differs from Gold and Silver, her shorts are now blue, her socks are now striped, and she wears a red bracelet on her arm.
It is also revealed in some of her artwork that Whitney opens her shirt when playing sports. Because of this, she wears a blue sports bra, revealing her belly.
In the games
When defeated, Whitney will start crying and will not give the Gym Badge. If the player walks away, a trainer will tell you to talk to her. After Whitney stops crying, she will give the Plain Badge and TM45 (Attract).
In the Anime
Whitney first appears in the episodes "A Goldenrod Opportunity", "A Dairy Tale Ending", and "Bagged then Tagged". At first glance Whitney is a kind girl, but she can be klutzy and ditzy sometimes, getting lost in her own town as an example. However, in battle she is quite formidable, especially with her Miltank.
According to a few in-game NPCs, Whitney only recently started training Pokémon and was so talented she was given the position of Gym Leader by the Pokémon League, despite her inexperince as a Trainer and slight immaturity (such as leaving the Gym to go to the Radio station to win a Radio Card and crying after she loses).