Madame Gabrielli may have been Henrietta, the wife of Antonio Gabrielli, FRGS (they were married in St Martin's in the Fields on 12 February 1852). At the time of the 1881 census they were living at 21 Queens Gate Terrace, London, with their daughter, A. Harriet M. Gabrielli. They were prosperous, with a lady's maid, two footmen, a cook and housemaid.
Another, rather more remote possibility is Giovanna or Girvanna Gabriella, who was recorded in the census in 1901 as a 63 year old Sicilian-born woman living in Fulham.
UK census 1881; UK census 1901.