Born a daughter of the Armstrong family, she married her first husband, Captain DeVane, at the age of fifteen, and had two sons by him, Paul and Edgar. Widowed at age twenty, she met her second husband, Gerard Grey, Earl of Melton, a year later. She had two sons by Grey, Harold and John. Her second husband died in an apparent suicide, and she did not marry again until her children were quite grown, to Sir George Stanley. She lives in Jermyn Street in London.
Benedicta hosts a musicale at her house in Jermyn Street, which is attended by Captain Stephan von Namtzen, Graf von Erdberg.
Benedicta is living in the Jermyn Street house with her niece and ward, Olivia. She set to marry Sir George Stanley, but breaks off the marriage when she believes someone is threatening her life and those of her sons.
Unbeknownest to either of her sons, Benedicta has been blackmailing Gilbert Rigby in order to find out who murdered her second husband, Gerard Grey.
After finding out that Bernard Adams is the murderer, she attempts to lure him to Jermyn Street, intending to force him to confess at gunpoint. However, John persuades her to allow him to apprehend Adams.
She and George are married not long afterward, on February 27th. Benedicta is later present for the christening of her namesake and granddaughter, Dorothea Jacqueline Benedicta.
John describes his mother as "kind but not particularly patient." She is very logical and plainspoken.
She is an avid reader with a penchant for slightly scandalous books like Fanny Hill and Les Bijoux Indiscrets.
Benedicta has pale blue eyes and fair hair. She is several inches shorter than her youngest son, who is himself described as below-average height.
She has a dimple that only shows when she is particularly amused.
- Benedicta is the feminine form of the late Latin name Benedictus, which meant "blessed".
- Armstrong comes from the Old English earm and strang, meaning "strong arm".
- DeVane is an Irish name originally written in a Gaelic form as O Daimhin, derived from the word damh, which refers to "an ox" or "a stag".
- Grey has two possible origins: 1) an Anglo-Saxon, Old English nickname for someone with grey hair or a grey beard, derived from the Old English pre 7th Century word "graeg", grey; 2) from the place called "Graye" in Calvados, Normandy, so called from the Old Gallo-Roman personal name "Gratus" meaning "Welcome" or "Pleasing", with the suffix "acum" meaning settlement or village.
- Stanley is from a place name meaning "stone clearing" in Old English.
- Gabaldon, Diana. "Lord John's Brothers-possible spoiler." MSG: 58458.2. Diana Gabaldon. Books and Writers Community. Compuserve. Published 7 January 2008. Accessed 26 August 2015.
- Age as of the end of Written in My Own Heart's Blood.
- Lord John and the Private Matter. . Benedicta is described as "several inches shorter than her youngest son," who is about 5'6".
- Gabaldon, Diana. "ECHO: Dottie and Henry." MSG: 66117.30. Diana Gabaldon. Books and Writers Community. Compuserve. Published 24 December 2009. Accessed 1 December 2017.
- Brotherhood of the Blade, Chapter 3
- Lord John and the Private Matter, Chapter 5
- Lord John and the Private Matter, Chapter 11
- Behind the Name: Benedicta. Accessed 10 May 2016.
- Behind the Name: Benedict. Accessed 10 May 2016.
- Behind the Name Surnames: Armstrong. Accessed 10 May 2016.
- House of Names: DeVane. Accessed 31 May 2016.
- Internet Surname Database: Grey. Accessed 19 June 2014.
- Behind the Name Surnames: Stanley. Accessed 03 June 2016.
- Lord John and the Brotherhood of the Blade, chapter 11.
- Lord John and the Brotherhood of the Blade, chapter 6.