Diana Parker is a character in Sanditon. She is the sister of Thomas, Susan, Sidney, and Arthur Parker. She is around about thirty-four years old, and though she claims to be an invalid, she is active and determined, especially in her promotion of Sanditon.
Diana writes Thomas soon after his return to Sanditon to sympathize over his recent injury and regale him with the illnesses recently suffered by herself, Susan, and Arthur. She reports that both a rich West Indian family and a girls' boarding school are coming to Sanditon, not realizing those two parties are one in the same.
Diana, Susan, and Arthur soon arrive in Sanditon themselves where they take lodgings. Diana's officiousness in the West Indian family's affairs, renting a house for them sight unseen, shocks Charlotte Heywood. She is shocked when she realizes the two parties are one, but she quickly recovers and continues her interference.
She encourages Mary Parker to ask Lady Denham to join a subscription for the impoverished Mullins family, and she furthermore suggests Mrs. Parker ask Lady Denham to join three other charitable causes. Realizing his wife is uncomfortable, Mr. Parker withdraws his request, forcing Diana to withdraw hers too.