I feel like I am now making progress.
Robert Peck was married twice. His second wife seems to have something of a story! Annie Kentfield (nicknamed "Queenie" and from a family of famous billiard players) was married three times. Notably her grandfather, Edwin Kentfield (1802-1873), was regarded as being one of the greatest billiard players of his time.
Firstly in 1874 to William Wallace Rodger-Cunliffe of Hadlow Castle. The couple divorced in 1880 due to her affair with William Arthur Hoare-Smith. She married Mr Hoare-Smith straight after the divorce. Their daughter Mildred Queenie Amelia Hoare-Smith was born on the 15 November 1879 in Jersey - thereby illegitimate. His family lived in Whimpole House in Devon.
The Hoare-Smith marriage collapsed due to Annie's affair with James Peck and her second divorce came in 1887. She married Peck in 1888. The took up residence at Howbury Hall soon after. When James Peck died in 1899 he left his entire estate (including his business) to Annie. She would die in 1902 in Bedford.
On the 1901 Census Mildred is listed as being a nurse at St. Bartholomew's Hospital in London. The photo below is in the photo album, so either a coincidence or it is Mildred?
There were two children, a boy and a girl, from Annie's first marriage. However, the daughter was unmarried and died in the United States
Mildred married a doctor named Leonard Gray on the 29 April 1908 in Malvern. His father had at one point been a clergyman in Bedford.
If the nurse is indeed Mildred, is she also the mystery woman who compiled the photo album? If this is the case then it would identify the women in the photo as being the Peck sisters, Annie, and Mildred? But maybe a big leap on my part!