Sister to Lord George Cavendish Bentinck. 1827 married John Evelyn Denison, 1st Viscount Ossington but left no children. When her brother (the eccentric 5th Duke) died with no male heir she and her sisters (including Lucy) inherited all the London property - Portland Place, Cavendish Square, Wimpole Street, Harley Street, Wigmore Street, etc. - a great wealth.
We thank Robert Throw who told us of the coffee tavern that the Viscountess gave to Newark, Nottinghamshire, in 1881, the town being close to her husband's ancestral seat. It was intended to provide for the working classes an alternative to the taverns that supplied the demon drink.
She also set up the Ossington Coffee Tavern at 22 & 24 Paradise Street, Marylebone. That street is now called Moxon Street and, if the numbering has not changed significantly, the building would have been on the north of the street at the western end, possibly the one now (2015) occupied by Le Vieux Comptoir.
She and her family's inheritance were central to the Druce Affair, a series of convoluted legal cases involving perjury, forgery, illegitimate children, alleged impersonations, funerals over lead-filled coffins and exhumations. All this went on 1896 - 1913.
Nottinghamshire History has a page about the lady.