The position is traditionally held by a female member of a noble family.
In the Middle Ages, Margaret of France, Queen of England, is noted to have had seven ladies-in-waiting: the three married ones were called Domina and the four unmarried maid of honour, but no principal lady-in-waiting is mentioned.
[1] During the Tudor dynasty (1485–1603), the First Lady of the Bedchamber was called Chief Gentlewoman of the Privy Chamber.
She had the highest rank among the Ladies of the bedchamber, and their role was to act as the attendants and companions of the royal woman.
[1] Under Elizabeth the role was also known as "Chief Gentlewoman of the Privy Chamber", for example during Parry's tenure of it.