Ladies of the Garter and Ladies of the Thistle
The two senior Orders of Chivalry, the Garter and the Thistle, are now both open to women. The first, and only, non-royal Lady Companion, the female equivalent of the Knights Companion, of the Order of the Garter was appointed in 1990. Lavinia, Duchess of Norfolk (now deceased) was already a peeress, so she did not bear the title of 'Lady', but she was entitled to use the post-nominal letters LG.
The first non-royal Lady Companion of the Thistle, Lady Marion Fraser, was appointed in 1996. If not already a peeress, or bearing the courtesy title of 'Lady', a woman who is appointed to the Order of the Garter or the Order of the Thistle bears the title of 'Lady' before her forename. Lady Marion Fraser, for example, the wife of Sir William Fraser, is now known as Lady Marion Fraser, LT (rather than Lady Fraser, LT).
Queen Alexandra was the first lady to receive the Order of the Garter (1901). Queen Mary and Queen Elizabeth (later Queen Elizabeth The Queen Mother) also received the Order upon becoming Queen Consort. The present Sovereign also received the Order in 1947 when Princess Elizabeth, Duchess of Edinburgh.
The only other ladies to receive (honorary) membership to the Order have been the late Queen Wilhelmina of The Netherlands, Queen (now Princess) Juliana and Queen Beatrix of The Netherlands, and Queen Margrethe II of Denmark. Queen Elizabeth The Queen Mother was appointed a Lady of the Order of the Thistle in King George VI's Coronation Honours List in 1937. The Princess Royal is also a Lady of the Thistle, but she bears the letters KT after her name.