Question: Who is the paternal grandmother of Lady Charlotte Finch?
Answer: Lady Sophia Osborne

Thomas Fermor, 1st Earl of Pomfret (1698–8 July 1753) was an English nobleman. He was the only son of William Fermor, 1st Baron Leominster by his third wife Lady Sophia Osborne. He succeeded to his father's barony on his death in 1711 as 2nd Baron Leominster