Bweek

Bweek is one of Tweek's sisters found in the Quackenheim Museum. She is on the Roquefort Diamonds, though after Chang rescues Xuan she will disappear with the diamonds into the basement.

How to Rescue
In order to rescue her, you will have to unlock the Vault, then glide across to her from the top of the room as she waits on top of the diamonds.