Okay,on the top of a ledge in route 2 in BW2,there will be a rich girl wearing a white dress standing and she will say to show some kind of Pokemon.What Pokemon should I show her?
The Lady wants to see a Pokemon with Solid Rock (Camerupt, Rhyperior, Tirtouga, Carracosta) and will give you a Dawn Stone if you oblige. Her request is the same in every copy of the game.
Unova Route 2 (Bulbapedia)
Talk to her again. She will mention an Ability. Bring her a Pokemon with that Ability.
Source: Tested on my White 2