British Ladies in Waiting

Mistress of the Robes and Groom of the Stole
Usually a duchess or a future duchess. Chief lady in waiting. Only a queen has a mistress of the robes
Ladies of the Bedchamber
Lady in waiting who is the wife of a peer
Women of the Bedchamber
Usually related to a titled family but a daughter who has not married a peer.

Extra refers to part time or someone who is only called for certain events such as a state banquet.

Bedchamber refers to the tradition when virtually the only only room that was private was a bedroom. It was therefore a position of influence where she could speak to the queen privately and ask for favours

The mistress of the robes was a role that included the job of ordering and caring for clothing which used to be incredibly valuable. She might also be given old clothing which could be sold for profit.