When Raven dresses up as "Piney," you can tell in one of the scenes her nails are painted, therefore they should have know it was an impersonator.
Donna Cabonna: Tiffany, were you eavesdropping?
Tiffany: Mostly dropping.
Donna: Raven! What were you doing up in those vents?!
Raven: Uh, Well, I heard you needed a new design for your fall line, so I said, 'Why not drop on in?'
Tiffany: 'Drop in'? More like 'Crash in'
Raven: I wouldn't have to crash in if you weren't hate-in.
Chelsea: Piney salute! From the ocean and the seas, to the forest and the trees. From the rivers great and small, to the moutaintops so tall. From all creatures great and slimy, we salute our founder Piney.
Raven: Maybe I can have my name next to yours.
Raven: In tiny little letters?
Raven: On the washing machine tag? We'll talk about it later.
(Raven, in disguise, has managed to halt the protest against using real fur on clothing)
Chelsea:: (ticked) Rae! I can't believe you did this!
Raven: (also ticked) I can't believe you care more about some fur thing than you do about me!
Chelsea: Rae, listen! You are super-talented! You'll get another shot like this, but the chinchillas won't!
Raven: (fuming) We're never gonna agree on this, are we?
Chelsea: I guess not. (Raven starts to walk away, fuming) Wait a minute: what does this mean? We can't be friends anymore?