This is not news.... she is already omitted from the Prichard-Jones and Nugent articles in the 2011 Debrett's, but his first wife, Heather Nugent, died 6 February 2010.
Heather Vivian Mary Nugent Prichard-Jones
Birth
1918
Dublin, County Dublin, Ireland
Death
6 Feb 2010 (aged 91–92)
Burial
Cremated, Location of ashes is unknown
https://www.findagrave.com/memorial/188515849/heather-vivian_mary-prichard-jonesextracts from obituaries, included on findagrave page:
"The death has occurred of Lady Heather PRICHARD-JONES (née Nugent)
Multyfarnham, Westmeath
Aged 92 years. A Memorial Mass, followed by the interment of her ashes, will be held on Saturday, July 24, 2010 at 12 noon in St. Nicholas' Parish Church, Multyfarnham, Co. Westmeath.
Date Published: Saturday 10th July 2010
Date of Death: Saturday 6th February 2010"
"Irish Party MP's daughter funeral
The funeral took place in Multyfarnham, Co Westmeath, of Lady Heather Prichard Jones, the first wife (divorced in 1950) of John Prichard Jones of Allenswood House, Lucan, Co Dublin.
Heather was the last surviving child of Walter Nugent, who lived at Multyfarnham and was Irish Party MP for South Westmeath from 1907 to 1918. It is believed that she was the last surviving child of a member of the Irish Parliamentary Party. In her later life she lived in London and was president of the Westmeath County Association there."