Who is Arabella Harlowe from Clarissa and what is their importance?

Arabella Harlowe is Clarissa's sister. Mr. Lovelace originally addressed Arabella when he began courting Clarissa, and she became jealous. She and James then colloborated to confine Clarissa and force her to marry Mr. Solmes. Arabella is described as haughty and impertinent, and she often insults her younger sister. She is remorseful when Clarissa dies, and she blames her involvement against her sister as part of the reason for her unhappiness later in life.