This plaque is in the tower entrance to Eversholt Church. Click for the full resolution version.

For the search engines, the text reads:
Sacred to the memory
of the
Honble Frances, Henley, Ongley,
eldest daughter of the
Right Honble Samuel, Henley, Lord Ongley,
of Old Warden, in the county of Bedford:
born the 22d of September 1764
and died the 24th of February 1823,
aged 58 years.The last tribute of esteem from a sincere friend.
L.M.
“L.M.” will have been Lucy Monoux.
There is a drawing of Frances in the National Portrait Gallery.
Frances seems to have lived at Linden with Lucy Monoux.
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