The Solicitor wrote a letter to Ann and _______ in which he asked us if we could settle the matter between _____?
The Solicitor wrote a letter to Ann and _______ in which he asked us if we could settle the matter between _____?
Explanation
The sentence should read: "The Solicitor wrote a letter to Ann and me in which he asked us if we could settle the matter between us."
"Me" is the correct object pronoun, while "us" is used correctly as the object of the preposition "between."